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2015-09-10mm: introduce idle page trackingVladimir Davydov
Knowing the portion of memory that is not used by a certain application or memory cgroup (idle memory) can be useful for partitioning the system efficiently, e.g. by setting memory cgroup limits appropriately. Currently, the only means to estimate the amount of idle memory provided by the kernel is /proc/PID/{clear_refs,smaps}: the user can clear the access bit for all pages mapped to a particular process by writing 1 to clear_refs, wait for some time, and then count smaps:Referenced. However, this method has two serious shortcomings: - it does not count unmapped file pages - it affects the reclaimer logic To overcome these drawbacks, this patch introduces two new page flags, Idle and Young, and a new sysfs file, /sys/kernel/mm/page_idle/bitmap. A page's Idle flag can only be set from userspace by setting bit in /sys/kernel/mm/page_idle/bitmap at the offset corresponding to the page, and it is cleared whenever the page is accessed either through page tables (it is cleared in page_referenced() in this case) or using the read(2) system call (mark_page_accessed()). Thus by setting the Idle flag for pages of a particular workload, which can be found e.g. by reading /proc/PID/pagemap, waiting for some time to let the workload access its working set, and then reading the bitmap file, one can estimate the amount of pages that are not used by the workload. The Young page flag is used to avoid interference with the memory reclaimer. A page's Young flag is set whenever the Access bit of a page table entry pointing to the page is cleared by writing to the bitmap file. If page_referenced() is called on a Young page, it will add 1 to its return value, therefore concealing the fact that the Access bit was cleared. Note, since there is no room for extra page flags on 32 bit, this feature uses extended page flags when compiled on 32 bit. [akpm@linux-foundation.org: fix build] [akpm@linux-foundation.org: kpageidle requires an MMU] [akpm@linux-foundation.org: decouple from page-flags rework] Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Michel Lespinasse <walken@google.com> Cc: David Rientjes <rientjes@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-10mmu-notifier: add clear_young callbackVladimir Davydov
In the scope of the idle memory tracking feature, which is introduced by the following patch, we need to clear the referenced/accessed bit not only in primary, but also in secondary ptes. The latter is required in order to estimate wss of KVM VMs. At the same time we want to avoid flushing tlb, because it is quite expensive and it won't really affect the final result. Currently, there is no function for clearing pte young bit that would meet our requirements, so this patch introduces one. To achieve that we have to add a new mmu-notifier callback, clear_young, since there is no method for testing-and-clearing a secondary pte w/o flushing tlb. The new method is not mandatory and currently only implemented by KVM. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Michel Lespinasse <walken@google.com> Cc: David Rientjes <rientjes@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-10memcg: zap try_get_mem_cgroup_from_pageVladimir Davydov
It is only used in mem_cgroup_try_charge, so fold it in and zap it. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Michel Lespinasse <walken@google.com> Cc: David Rientjes <rientjes@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-10hwpoison: use page_cgroup_ino for filtering by memcgVladimir Davydov
Hwpoison allows to filter pages by memory cgroup ino. Currently, it calls try_get_mem_cgroup_from_page to obtain the cgroup from a page and then its ino using cgroup_ino, but now we have a helper method for that, page_cgroup_ino, so use it instead. This patch also loosens the hwpoison memcg filter dependency rules - it makes it depend on CONFIG_MEMCG instead of CONFIG_MEMCG_SWAP, because hwpoison memcg filter does not require anything (nor it used to) from CONFIG_MEMCG_SWAP side. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Michel Lespinasse <walken@google.com> Cc: David Rientjes <rientjes@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-10memcg: add page_cgroup_ino helperVladimir Davydov
This patchset introduces a new user API for tracking user memory pages that have not been used for a given period of time. The purpose of this is to provide the userspace with the means of tracking a workload's working set, i.e. the set of pages that are actively used by the workload. Knowing the working set size can be useful for partitioning the system more efficiently, e.g. by tuning memory cgroup limits appropriately, or for job placement within a compute cluster. ==== USE CASES ==== The unified cgroup hierarchy has memory.low and memory.high knobs, which are defined as the low and high boundaries for the workload working set size. However, the working set size of a workload may be unknown or change in time. With this patch set, one can periodically estimate the amount of memory unused by each cgroup and tune their memory.low and memory.high parameters accordingly, therefore optimizing the overall memory utilization. Another use case is balancing workloads within a compute cluster. Knowing how much memory is not really used by a workload unit may help take a more optimal decision when considering migrating the unit to another node within the cluster. Also, as noted by Minchan, this would be useful for per-process reclaim (https://lwn.net/Articles/545668/). With idle tracking, we could reclaim idle pages only by smart user memory manager. ==== USER API ==== The user API consists of two new files: * /sys/kernel/mm/page_idle/bitmap. This file implements a bitmap where each bit corresponds to a page, indexed by PFN. When the bit is set, the corresponding page is idle. A page is considered idle if it has not been accessed since it was marked idle. To mark a page idle one should set the bit corresponding to the page by writing to the file. A value written to the file is OR-ed with the current bitmap value. Only user memory pages can be marked idle, for other page types input is silently ignored. Writing to this file beyond max PFN results in the ENXIO error. Only available when CONFIG_IDLE_PAGE_TRACKING is set. This file can be used to estimate the amount of pages that are not used by a particular workload as follows: 1. mark all pages of interest idle by setting corresponding bits in the /sys/kernel/mm/page_idle/bitmap 2. wait until the workload accesses its working set 3. read /sys/kernel/mm/page_idle/bitmap and count the number of bits set * /proc/kpagecgroup. This file contains a 64-bit inode number of the memory cgroup each page is charged to, indexed by PFN. Only available when CONFIG_MEMCG is set. This file can be used to find all pages (including unmapped file pages) accounted to a particular cgroup. Using /sys/kernel/mm/page_idle/bitmap, one can then estimate the cgroup working set size. For an example of using these files for estimating the amount of unused memory pages per each memory cgroup, please see the script attached below. ==== REASONING ==== The reason to introduce the new user API instead of using /proc/PID/{clear_refs,smaps} is that the latter has two serious drawbacks: - it does not count unmapped file pages - it affects the reclaimer logic The new API attempts to overcome them both. For more details on how it is achieved, please see the comment to patch 6. ==== PATCHSET STRUCTURE ==== The patch set is organized as follows: - patch 1 adds page_cgroup_ino() helper for the sake of /proc/kpagecgroup and patches 2-3 do related cleanup - patch 4 adds /proc/kpagecgroup, which reports cgroup ino each page is charged to - patch 5 introduces a new mmu notifier callback, clear_young, which is a lightweight version of clear_flush_young; it is used in patch 6 - patch 6 implements the idle page tracking feature, including the userspace API, /sys/kernel/mm/page_idle/bitmap - patch 7 exports idle flag via /proc/kpageflags ==== SIMILAR WORKS ==== Originally, the patch for tracking idle memory was proposed back in 2011 by Michel Lespinasse (see http://lwn.net/Articles/459269/). The main difference between Michel's patch and this one is that Michel implemented a kernel space daemon for estimating idle memory size per cgroup while this patch only provides the userspace with the minimal API for doing the job, leaving the rest up to the userspace. However, they both share the same idea of Idle/Young page flags to avoid affecting the reclaimer logic. ==== PERFORMANCE EVALUATION ==== SPECjvm2008 (https://www.spec.org/jvm2008/) was used to evaluate the performance impact introduced by this patch set. Three runs were carried out: - base: kernel without the patch - patched: patched kernel, the feature is not used - patched-active: patched kernel, 1 minute-period daemon is used for tracking idle memory For tracking idle memory, idlememstat utility was used: https://github.com/locker/idlememstat testcase base patched patched-active compiler 537.40 ( 0.00)% 532.26 (-0.96)% 538.31 ( 0.17)% compress 305.47 ( 0.00)% 301.08 (-1.44)% 300.71 (-1.56)% crypto 284.32 ( 0.00)% 282.21 (-0.74)% 284.87 ( 0.19)% derby 411.05 ( 0.00)% 413.44 ( 0.58)% 412.07 ( 0.25)% mpegaudio 189.96 ( 0.00)% 190.87 ( 0.48)% 189.42 (-0.28)% scimark.large 46.85 ( 0.00)% 46.41 (-0.94)% 47.83 ( 2.09)% scimark.small 412.91 ( 0.00)% 415.41 ( 0.61)% 421.17 ( 2.00)% serial 204.23 ( 0.00)% 213.46 ( 4.52)% 203.17 (-0.52)% startup 36.76 ( 0.00)% 35.49 (-3.45)% 35.64 (-3.05)% sunflow 115.34 ( 0.00)% 115.08 (-0.23)% 117.37 ( 1.76)% xml 620.55 ( 0.00)% 619.95 (-0.10)% 620.39 (-0.03)% composite 211.50 ( 0.00)% 211.15 (-0.17)% 211.67 ( 0.08)% time idlememstat: 17.20user 65.16system 2:15:23elapsed 1%CPU (0avgtext+0avgdata 8476maxresident)k 448inputs+40outputs (1major+36052minor)pagefaults 0swaps ==== SCRIPT FOR COUNTING IDLE PAGES PER CGROUP ==== #! /usr/bin/python # import os import stat import errno import struct CGROUP_MOUNT = "/sys/fs/cgroup/memory" BUFSIZE = 8 * 1024 # must be multiple of 8 def get_hugepage_size(): with open("/proc/meminfo", "r") as f: for s in f: k, v = s.split(":") if k == "Hugepagesize": return int(v.split()[0]) * 1024 PAGE_SIZE = os.sysconf("SC_PAGE_SIZE") HUGEPAGE_SIZE = get_hugepage_size() def set_idle(): f = open("/sys/kernel/mm/page_idle/bitmap", "wb", BUFSIZE) while True: try: f.write(struct.pack("Q", pow(2, 64) - 1)) except IOError as err: if err.errno == errno.ENXIO: break raise f.close() def count_idle(): f_flags = open("/proc/kpageflags", "rb", BUFSIZE) f_cgroup = open("/proc/kpagecgroup", "rb", BUFSIZE) with open("/sys/kernel/mm/page_idle/bitmap", "rb", BUFSIZE) as f: while f.read(BUFSIZE): pass # update idle flag idlememsz = {} while True: s1, s2 = f_flags.read(8), f_cgroup.read(8) if not s1 or not s2: break flags, = struct.unpack('Q', s1) cgino, = struct.unpack('Q', s2) unevictable = (flags >> 18) & 1 huge = (flags >> 22) & 1 idle = (flags >> 25) & 1 if idle and not unevictable: idlememsz[cgino] = idlememsz.get(cgino, 0) + \ (HUGEPAGE_SIZE if huge else PAGE_SIZE) f_flags.close() f_cgroup.close() return idlememsz if __name__ == "__main__": print "Setting the idle flag for each page..." set_idle() raw_input("Wait until the workload accesses its working set, " "then press Enter") print "Counting idle pages..." idlememsz = count_idle() for dir, subdirs, files in os.walk(CGROUP_MOUNT): ino = os.stat(dir)[stat.ST_INO] print dir + ": " + str(idlememsz.get(ino, 0) / 1024) + " kB" ==== END SCRIPT ==== This patch (of 8): Add page_cgroup_ino() helper to memcg. This function returns the inode number of the closest online ancestor of the memory cgroup a page is charged to. It is required for exporting information about which page is charged to which cgroup to userspace, which will be introduced by a following patch. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Michel Lespinasse <walken@google.com> Cc: David Rientjes <rientjes@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-10zswap: change zpool/compressor at runtimeDan Streetman
Update the zpool and compressor parameters to be changeable at runtime. When changed, a new pool is created with the requested zpool/compressor, and added as the current pool at the front of the pool list. Previous pools remain in the list only to remove existing compressed pages from. The old pool(s) are removed once they become empty. Signed-off-by: Dan Streetman <ddstreet@ieee.org> Acked-by: Seth Jennings <sjennings@variantweb.net> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-10zswap: dynamic pool creationDan Streetman
Add dynamic creation of pools. Move the static crypto compression per-cpu transforms into each pool. Add a pointer to zswap_entry to the pool it's in. This is required by the following patch which enables changing the zswap zpool and compressor params at runtime. [akpm@linux-foundation.org: fix merge snafus] Signed-off-by: Dan Streetman <ddstreet@ieee.org> Acked-by: Seth Jennings <sjennings@variantweb.net> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-10zpool: add zpool_has_pool()Dan Streetman
This series makes creation of the zpool and compressor dynamic, so that they can be changed at runtime. This makes using/configuring zswap easier, as before this zswap had to be configured at boot time, using boot params. This uses a single list to track both the zpool and compressor together, although Seth had mentioned an alternative which is to track the zpools and compressors using separate lists. In the most common case, only a single zpool and single compressor, using one list is slightly simpler than using two lists, and for the uncommon case of multiple zpools and/or compressors, using one list is slightly less simple (and uses slightly more memory, probably) than using two lists. This patch (of 4): Add zpool_has_pool() function, indicating if the specified type of zpool is available (i.e. zsmalloc or zbud). This allows checking if a pool is available, without actually trying to allocate it, similar to crypto_has_alg(). This is used by a following patch to zswap that enables the dynamic runtime creation of zswap zpools. Signed-off-by: Dan Streetman <ddstreet@ieee.org> Acked-by: Seth Jennings <sjennings@variantweb.net> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08Merge branch 'akpm' (patches from Andrew)Linus Torvalds
Merge second patch-bomb from Andrew Morton: "Almost all of the rest of MM. There was an unusually large amount of MM material this time" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (141 commits) zpool: remove no-op module init/exit mm: zbud: constify the zbud_ops mm: zpool: constify the zpool_ops mm: swap: zswap: maybe_preload & refactoring zram: unify error reporting zsmalloc: remove null check from destroy_handle_cache() zsmalloc: do not take class lock in zs_shrinker_count() zsmalloc: use class->pages_per_zspage zsmalloc: consider ZS_ALMOST_FULL as migrate source zsmalloc: partial page ordering within a fullness_list zsmalloc: use shrinker to trigger auto-compaction zsmalloc: account the number of compacted pages zsmalloc/zram: introduce zs_pool_stats api zsmalloc: cosmetic compaction code adjustments zsmalloc: introduce zs_can_compact() function zsmalloc: always keep per-class stats zsmalloc: drop unused variable `nr_to_migrate' mm/memblock.c: fix comment in __next_mem_range() mm/page_alloc.c: fix type information of memoryless node memory-hotplug: fix comments in zone_spanned_pages_in_node() and zone_spanned_pages_in_node() ...
2015-09-08zpool: remove no-op module init/exitDan Streetman
Remove zpool_init() and zpool_exit(); they do nothing other than print "loaded" and "unloaded". Signed-off-by: Dan Streetman <ddstreet@ieee.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm: zbud: constify the zbud_opsKrzysztof Kozlowski
The structure zbud_ops is not modified so make the pointer to it a pointer to const. Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> Acked-by: Dan Streetman <ddstreet@ieee.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm: zpool: constify the zpool_opsKrzysztof Kozlowski
The structure zpool_ops is not modified so make the pointer to it a pointer to const. Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> Acked-by: Dan Streetman <ddstreet@ieee.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm: swap: zswap: maybe_preload & refactoringDmitry Safonov
zswap_get_swap_cache_page and read_swap_cache_async have pretty much the same code with only significant difference in return value and usage of swap_readpage. I a helper __read_swap_cache_async() with the common code. Behavior change: now zswap_get_swap_cache_page will use radix_tree_maybe_preload instead radix_tree_preload. Looks like, this wasn't changed only by the reason of code duplication. Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@fb.com> Cc: Christoph Hellwig <hch@lst.de> Cc: David Herrmann <dh.herrmann@gmail.com> Cc: Seth Jennings <sjennings@variantweb.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: remove null check from destroy_handle_cache()Sergey Senozhatsky
We can pass a NULL cache pointer to kmem_cache_destroy(), because it NULL-checks its argument now. Remove redundant test from destroy_handle_cache(). Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: do not take class lock in zs_shrinker_count()Sergey Senozhatsky
We can avoid taking class ->lock around zs_can_compact() in zs_shrinker_count(), because the number that we return back is outdated in general case, by design. We have different sources that are able to change class's state right after we return from zs_can_compact() -- ongoing I/O operations, manually triggered compaction, or two of them happening simultaneously. We re-do this calculations during compaction on a per class basis anyway. zs_unregister_shrinker() will not return until we have an active shrinker, so classes won't unexpectedly disappear while zs_shrinker_count() iterates them. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: use class->pages_per_zspageMinchan Kim
There is no need to recalcurate pages_per_zspage in runtime. Just use class->pages_per_zspage to avoid unnecessary runtime overhead. Signed-off-by: Minchan Kim <minchan@kernel.org> Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: consider ZS_ALMOST_FULL as migrate sourceMinchan Kim
There is no reason to prevent select ZS_ALMOST_FULL as migration source if we cannot find source from ZS_ALMOST_EMPTY. With this patch, zs_can_compact will return more exact result. Signed-off-by: Minchan Kim <minchan.kim@lge.com> Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: partial page ordering within a fullness_listSergey Senozhatsky
We want to see more ZS_FULL pages and less ZS_ALMOST_{FULL, EMPTY} pages. Put a page with higher ->inuse count first within its ->fullness_list, which will give us better chances to fill up this page with new objects (find_get_zspage() return ->fullness_list head for new object allocation), so some zspages will become ZS_ALMOST_FULL/ZS_FULL quicker. It performs a trivial and cheap ->inuse compare which does not slow down zsmalloc and in the worst case keeps the list pages in no particular order. A more expensive solution could sort fullness_list by ->inuse count. [minchan@kernel.org: code adjustments] Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: use shrinker to trigger auto-compactionSergey Senozhatsky
Perform automatic pool compaction by a shrinker when system is getting tight on memory. User-space has a very little knowledge regarding zsmalloc fragmentation and basically has no mechanism to tell whether compaction will result in any memory gain. Another issue is that user space is not always aware of the fact that system is getting tight on memory. Which leads to very uncomfortable scenarios when user space may start issuing compaction 'randomly' or from crontab (for example). Fragmentation is not always necessarily bad, allocated and unused objects, after all, may be filled with the data later, w/o the need of allocating a new zspage. On the other hand, we obviously don't want to waste memory when the system needs it. Compaction now has a relatively quick pool scan so we are able to estimate the number of pages that will be freed easily, which makes it possible to call this function from a shrinker->count_objects() callback. We also abort compaction as soon as we detect that we can't free any pages any more, preventing wasteful objects migrations. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Suggested-by: Minchan Kim <minchan@kernel.org> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: account the number of compacted pagesSergey Senozhatsky
Compaction returns back to zram the number of migrated objects, which is quite uninformative -- we have objects of different sizes so user space cannot obtain any valuable data from that number. Change compaction to operate in terms of pages and return back to compaction issuer the number of pages that were freed during compaction. So from now on we will export more meaningful value in zram<id>/mm_stat -- the number of freed (compacted) pages. This requires: (a) a rename of `num_migrated' to 'pages_compacted' (b) a internal API change -- return first_page's fullness_group from putback_zspage(), so we know when putback_zspage() did free_zspage(). It helps us to account compaction stats correctly. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc/zram: introduce zs_pool_stats apiSergey Senozhatsky
`zs_compact_control' accounts the number of migrated objects but it has a limited lifespan -- we lose it as soon as zs_compaction() returns back to zram. It worked fine, because (a) zram had it's own counter of migrated objects and (b) only zram could trigger compaction. However, this does not work for automatic pool compaction (not issued by zram). To account objects migrated during auto-compaction (issued by the shrinker) we need to store this number in zs_pool. Define a new `struct zs_pool_stats' structure to keep zs_pool's stats there. It provides only `num_migrated', as of this writing, but it surely can be extended. A new zsmalloc zs_pool_stats() symbol exports zs_pool's stats back to caller. Use zs_pool_stats() in zram and remove `num_migrated' from zram_stats. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Suggested-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: cosmetic compaction code adjustmentsSergey Senozhatsky
Change zs_object_copy() argument order to be (DST, SRC) rather than (SRC, DST). copy/move functions usually have (to, from) arguments order. Rename alloc_target_page() to isolate_target_page(). This function doesn't allocate anything, it isolates target page, pretty much like isolate_source_page(). Tweak __zs_compact() comment. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: introduce zs_can_compact() functionSergey Senozhatsky
This function checks if class compaction will free any pages. Rephrasing -- do we have enough unused objects to form at least one ZS_EMPTY page and free it. It aborts compaction if class compaction will not result in any (further) savings. EXAMPLE (this debug output is not part of this patch set): - class size - number of allocated objects - number of used objects - max objects per zspage - pages per zspage - estimated number of pages that will be freed [..] class-512 objs:544 inuse:540 maxobj-per-zspage:8 pages-per-zspage:1 zspages-to-free:0 ... class-512 compaction is useless. break class-496 objs:660 inuse:570 maxobj-per-zspage:33 pages-per-zspage:4 zspages-to-free:2 class-496 objs:627 inuse:570 maxobj-per-zspage:33 pages-per-zspage:4 zspages-to-free:1 class-496 objs:594 inuse:570 maxobj-per-zspage:33 pages-per-zspage:4 zspages-to-free:0 ... class-496 compaction is useless. break class-448 objs:657 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:4 class-448 objs:648 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:3 class-448 objs:639 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:2 class-448 objs:630 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:1 class-448 objs:621 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:0 ... class-448 compaction is useless. break class-432 objs:728 inuse:685 maxobj-per-zspage:28 pages-per-zspage:3 zspages-to-free:1 class-432 objs:700 inuse:685 maxobj-per-zspage:28 pages-per-zspage:3 zspages-to-free:0 ... class-432 compaction is useless. break class-416 objs:819 inuse:705 maxobj-per-zspage:39 pages-per-zspage:4 zspages-to-free:2 class-416 objs:780 inuse:705 maxobj-per-zspage:39 pages-per-zspage:4 zspages-to-free:1 class-416 objs:741 inuse:705 maxobj-per-zspage:39 pages-per-zspage:4 zspages-to-free:0 ... class-416 compaction is useless. break class-400 objs:690 inuse:674 maxobj-per-zspage:10 pages-per-zspage:1 zspages-to-free:1 class-400 objs:680 inuse:674 maxobj-per-zspage:10 pages-per-zspage:1 zspages-to-free:0 ... class-400 compaction is useless. break class-384 objs:736 inuse:709 maxobj-per-zspage:32 pages-per-zspage:3 zspages-to-free:0 ... class-384 compaction is useless. break [..] Every "compaction is useless" indicates that we saved CPU cycles. class-512 has 544 object allocated 540 objects used 8 objects per-page Even if we have a ALMOST_EMPTY zspage, we still don't have enough room to migrate all of its objects and free this zspage; so compaction will not make a lot of sense, it's better to just leave it as is. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: always keep per-class statsSergey Senozhatsky
Always account per-class `zs_size_stat' stats. This data will help us make better decisions during compaction. We are especially interested in OBJ_ALLOCATED and OBJ_USED, which can tell us if class compaction will result in any memory gain. For instance, we know the number of allocated objects in the class, the number of objects being used (so we also know how many objects are not used) and the number of objects per-page. So we can ensure if we have enough unused objects to form at least one ZS_EMPTY zspage during compaction. We calculate this value on per-class basis so we can calculate a total number of zspages that can be released. Which is exactly what a shrinker wants to know. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08zsmalloc: drop unused variable `nr_to_migrate'Sergey Senozhatsky
This patchset tweaks compaction and makes it possible to trigger pool compaction automatically when system is getting low on memory. zsmalloc in some cases can suffer from a notable fragmentation and compaction can release some considerable amount of memory. The problem here is that currently we fully rely on user space to perform compaction when needed. However, performing zsmalloc compaction is not always an obvious thing to do. For example, suppose we have a `idle' fragmented (compaction was never performed) zram device and system is getting low on memory due to some 3rd party user processes (gcc LTO, or firefox, etc.). It's quite unlikely that user space will issue zpool compaction in this case. Besides, user space cannot tell for sure how badly pool is fragmented; however, this info is known to zsmalloc and, hence, to a shrinker. This patch (of 7): __zs_compact() does not use `nr_to_migrate', drop it. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/memblock.c: fix comment in __next_mem_range()Alexander Kuleshov
Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/page_alloc.c: fix type information of memoryless nodeZhen Lei
For a memoryless node, the output of get_pfn_range_for_nid are all zero. It will display mem from 0 to -1. Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08memory-hotplug: fix comments in zone_spanned_pages_in_node() and ↵Xishi Qiu
zone_spanned_pages_in_node() When hot adding a node from add_memory(), we will add memblock first, so the node is not empty. But when called from cpu_up(), the node should be empty. Signed-off-by: Xishi Qiu <qiuxishi@huawei.com> Cc: Tang Chen <tangchen@cn.fujitsu.com> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>\ Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/page_alloc.c: change sysctl_lower_zone_reserve_ratio to ↵Yaowei Bai
sysctl_lowmem_reserve_ratio in comments We use sysctl_lowmem_reserve_ratio rather than sysctl_lower_zone_reserve_ratio to determine how aggressive the kernel is in defending lowmem from the possibility of being captured into pinned user memory. To avoid misleading, correct it in some comments. Signed-off-by: Yaowei Bai <bywxiaobai@163.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/page_alloc.c: fix a misleading commentYaowei Bai
The comment says that the per-cpu batchsize and zone watermarks are determined by present_pages which is definitely wrong, they are both calculated from managed_pages. Fix it. Signed-off-by: Yaowei Bai <bywxiaobai@163.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/mmap.c:insert_vm_struct(): check for failure before setting valuesChen Gang
There's no point in initializing vma->vm_pgoff if the insertion attempt will be failing anyway. Run the checks before performing the initialization. Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/khugepaged: allow interruption of allocation sleep againPetr Mladek
Commit 1dfb059b9438 ("thp: reduce khugepaged freezing latency") fixed khugepaged to do not block a system suspend. But the result is that it could not get interrupted before the given timeout because the condition for the wait event is "false". This patch puts back the original approach but it uses freezable_schedule_timeout_interruptible() instead of schedule_timeout_interruptible(). It does the right thing. I am pretty sure that the freezable variant was not used in the original fix only because it was not available at that time. The regression has been there for ages. It was not critical. It just did the allocation throttling a little bit more aggressively. I found this problem when converting the kthread to kthread worker API and trying to understand the code. This bug is thought to have minimal userspace-visible impact. Somebody could set a high alloc_sleep value by mistake, and then try to fix it back, but khugepaged would keep sleeping until the high value expires. Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: David Rientjes <rientjes@google.com> Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/memblock.c: fiy typos in commentsAlexander Kuleshov
s/succees/success/ Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/compaction: correct to flush migrated pages if pageblock skip happensJoonsoo Kim
We cache isolate_start_pfn before entering isolate_migratepages(). If pageblock is skipped in isolate_migratepages() due to whatever reason, cc->migrate_pfn can be far from isolate_start_pfn hence we flush pages that were freed. For example, the following scenario can be possible: - assume order-9 compaction, pageblock order is 9 - start_isolate_pfn is 0x200 - isolate_migratepages() - skip a number of pageblocks - start to isolate from pfn 0x600 - cc->migrate_pfn = 0x620 - return - last_migrated_pfn is set to 0x200 - check flushing condition - current_block_start is set to 0x600 - last_migrated_pfn < current_block_start then do useless flush This wrong flush would not help the performance and success rate so this patch tries to fix it. One simple way to know the exact position where we start to isolate migratable pages is that we cache it in isolate_migratepages() before entering actual isolation. This patch implements that and fixes the problem. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm: rename alloc_pages_exact_node() to __alloc_pages_node()Vlastimil Babka
alloc_pages_exact_node() was introduced in commit 6484eb3e2a81 ("page allocator: do not check NUMA node ID when the caller knows the node is valid") as an optimized variant of alloc_pages_node(), that doesn't fallback to current node for nid == NUMA_NO_NODE. Unfortunately the name of the function can easily suggest that the allocation is restricted to the given node and fails otherwise. In truth, the node is only preferred, unless __GFP_THISNODE is passed among the gfp flags. The misleading name has lead to mistakes in the past, see for example commits 5265047ac301 ("mm, thp: really limit transparent hugepage allocation to local node") and b360edb43f8e ("mm, mempolicy: migrate_to_node should only migrate to node"). Another issue with the name is that there's a family of alloc_pages_exact*() functions where 'exact' means exact size (instead of page order), which leads to more confusion. To prevent further mistakes, this patch effectively renames alloc_pages_exact_node() to __alloc_pages_node() to better convey that it's an optimized variant of alloc_pages_node() not intended for general usage. Both functions get described in comments. It has been also considered to really provide a convenience function for allocations restricted to a node, but the major opinion seems to be that __GFP_THISNODE already provides that functionality and we shouldn't duplicate the API needlessly. The number of users would be small anyway. Existing callers of alloc_pages_exact_node() are simply converted to call __alloc_pages_node(), with the exception of sba_alloc_coherent() which open-codes the check for NUMA_NO_NODE, so it is converted to use alloc_pages_node() instead. This means it no longer performs some VM_BUG_ON checks, and since the current check for nid in alloc_pages_node() uses a 'nid < 0' comparison (which includes NUMA_NO_NODE), it may hide wrong values which would be previously exposed. Both differences will be rectified by the next patch. To sum up, this patch makes no functional changes, except temporarily hiding potentially buggy callers. Restricting the checks in alloc_pages_node() is left for the next patch which can in turn expose more existing buggy callers. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Robin Holt <robinmholt@gmail.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Christoph Lameter <cl@linux.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Cc: Mel Gorman <mgorman@suse.de> Cc: David Rientjes <rientjes@google.com> Cc: Greg Thelen <gthelen@google.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Gleb Natapov <gleb@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Cliff Whickman <cpw@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm, vmscan: unlock page while waiting on writebackHugh Dickins
This is merely a politeness: I've not found that shrink_page_list() leads to deadlock with the page it holds locked across wait_on_page_writeback(); but nevertheless, why hold others off by keeping the page locked there? And while we're at it: remove the mistaken "not " from the commentary on this Case 3 (and a distracting blank line from Case 2, if I may). Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08list_lru: don't call list_lru_from_kmem if the list_head is emptyJeff Layton
If the list_head is empty then we'll have called list_lru_from_kmem for nothing. Move that call inside of the list_empty if block. Signed-off-by: Jeff Layton <jeff.layton@primarydata.com> Reviewed-by: Vladimir Davydov <vdavydov@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08kmemleak: record accurate early log buffer count and report when exceededWang Kai
In log_early function, crt_early_log should also count once when 'crt_early_log >= ARRAY_SIZE(early_log)'. Otherwise the reported count from kmemleak_init is one less than 'actual number'. Then, in kmemleak_init, if early_log buffer size equal actual number, kmemleak will init sucessful, so change warning condition to 'crt_early_log > ARRAY_SIZE(early_log)'. Signed-off-by: Wang Kai <morgan.wang@huawei.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/mmap.c: simplify the failure return working flowChen Gang
__split_vma() doesn't need out_err label, neither need initializing err. copy_vma() can return NULL directly when kmem_cache_alloc() fails. Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08shmem: recalculate file inode when fstatYu Zhao
Shmem uses shmem_recalc_inode to update i_blocks when it allocates page, undoes range or swaps. But mm can drop clean page without notifying shmem. This makes fstat sometimes return out-of-date block size. The problem can be partially solved when we add inode_operations->getattr which calls shmem_recalc_inode to update i_blocks for fstat. shmem_recalc_inode also updates counter used by statfs and vm_committed_as. For them the situation is not changed. They still suffer from the discrepancy after dropping clean page and before the function is called by aforementioned triggers. Signed-off-by: Yu Zhao <yuzhao@google.com> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/memblock.c: rename local variable of memblock_type to 'type'Alexander Kuleshov
Since commit e3239ff92a17 ("memblock: Rename memblock_region to memblock_type and memblock_property to memblock_region"), all local variables of the membock_type type were renamed to 'type'. This commit renames all remaining local variables with the memblock_type type to the same view. Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/hwpoison: don't try to unpoison containment-failed pagesNaoya Horiguchi
memory_failure() can be called at any page at any time, which means that we can't eliminate the possibility of containment failure. In such case the best option is to leak the page intentionally (and never touch it later.) We have an unpoison function for testing, and it cannot handle such containment-failed pages, which results in kernel panic (visible with various calltraces.) So this patch suggests that we limit the unpoisonable pages to properly contained pages and ignore any other ones. Testers are recommended to keep in mind that there're un-unpoisonable pages when writing test programs. Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Tested-by: Wanpeng Li <wanpeng.li@hotmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/hwpoison: fix race between soft_offline_page and unpoison_memoryWanpeng Li
Wanpeng Li reported a race between soft_offline_page() and unpoison_memory(), which causes the following kernel panic: BUG: Bad page state in process bash pfn:97000 page:ffffea00025c0000 count:0 mapcount:1 mapping: (null) index:0x7f4fdbe00 flags: 0x1fffff80080048(uptodate|active|swapbacked) page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set bad because of flags: flags: 0x40(active) Modules linked in: snd_hda_codec_hdmi i915 rpcsec_gss_krb5 nfsv4 dns_resolver bnep rfcomm nfsd bluetooth auth_rpcgss nfs_acl nfs rfkill lockd grace sunrpc i2c_algo_bit drm_kms_helper snd_hda_codec_realtek snd_hda_codec_generic drm snd_hda_intel fscache snd_hda_codec x86_pkg_temp_thermal coretemp kvm_intel snd_hda_core snd_hwdep kvm snd_pcm snd_seq_dummy snd_seq_oss crct10dif_pclmul snd_seq_midi crc32_pclmul snd_seq_midi_event ghash_clmulni_intel snd_rawmidi aesni_intel lrw gf128mul snd_seq glue_helper ablk_helper snd_seq_device cryptd fuse snd_timer dcdbas serio_raw mei_me parport_pc snd mei ppdev i2c_core video lp soundcore parport lpc_ich shpchp mfd_core ext4 mbcache jbd2 sd_mod e1000e ahci ptp libahci crc32c_intel libata pps_core CPU: 3 PID: 2211 Comm: bash Not tainted 4.2.0-rc5-mm1+ #45 Hardware name: Dell Inc. OptiPlex 7020/0F5C5X, BIOS A03 01/08/2015 Call Trace: dump_stack+0x48/0x5c bad_page+0xe6/0x140 free_pages_prepare+0x2f9/0x320 ? uncharge_list+0xdd/0x100 free_hot_cold_page+0x40/0x170 __put_single_page+0x20/0x30 put_page+0x25/0x40 unmap_and_move+0x1a6/0x1f0 migrate_pages+0x100/0x1d0 ? kill_procs+0x100/0x100 ? unlock_page+0x6f/0x90 __soft_offline_page+0x127/0x2a0 soft_offline_page+0xa6/0x200 This race is explained like below: CPU0 CPU1 soft_offline_page __soft_offline_page TestSetPageHWPoison unpoison_memory PageHWPoison check (true) TestClearPageHWPoison put_page -> release refcount held by get_hwpoison_page in unpoison_memory put_page -> release refcount held by isolate_lru_page in __soft_offline_page migrate_pages The second put_page() releases refcount held by isolate_lru_page() which will lead to unmap_and_move() releases the last refcount of page and w/ mapcount still 1 since try_to_unmap() is not called if there is only one user map the page. Anyway, the page refcount and mapcount will still mess if the page is mapped by multiple users. This race was introduced by commit 4491f71260 ("mm/memory-failure: set PageHWPoison before migrate_pages()"), which focuses on preventing the reuse of successfully migrated page. Before this commit we prevent the reuse by changing the migratetype to MIGRATE_ISOLATE during soft offlining, which has the following problems, so simply reverting the commit is not a best option: 1) it doesn't eliminate the reuse completely, because set_migratetype_isolate() can fail to set MIGRATE_ISOLATE to the target page if the pageblock of the page contains one or more unmovable pages (i.e. has_unmovable_pages() returns true). 2) the original code changes migratetype to MIGRATE_ISOLATE forcibly, and sets it to MIGRATE_MOVABLE forcibly after soft offline, regardless of the original migratetype state, which could impact other subsystems like memory hotplug or compaction. This patch moves PageSetHWPoison just after put_page() in unmap_and_move(), which closes up the reported race window and minimizes another race window b/w SetPageHWPoison and reallocation (which causes the reuse of soft-offlined page.) The latter race window still exists but it's acceptable, because it's rare and effectively the same as ordinary "containment failure" case even if it happens, so keep the window open is acceptable. Fixes: 4491f71260 ("mm/memory-failure: set PageHWPoison before migrate_pages()") Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reported-by: Wanpeng Li <wanpeng.li@hotmail.com> Tested-by: Wanpeng Li <wanpeng.li@hotmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/hwpoison: introduce num_poisoned_pages wrappersNaoya Horiguchi
num_poisoned_pages counter will be changed outside mm/memory-failure.c by a subsequent patch, so this patch prepares wrappers to manipulate it. Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Tested-by: Wanpeng Li <wanpeng.li@hotmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/hwpoison: replace most of put_page in memory error handling by ↵Wanpeng Li
put_hwpoison_page Replace most instances of put_page() in memory error handling with put_hwpoison_page(). Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/hwpoison: fix refcount of THP head page in no-injection caseWanpeng Li
Hwpoison injection takes a refcount of target page and another refcount of head page of THP if the target page is the tail page of a THP. However, current code doesn't release the refcount of head page if the THP is not supported to be injected wrt hwpoison filter. Fix it by reducing the refcount of head page if the target page is the tail page of a THP and it is not supported to be injected. Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/hwpoison: introduce put_hwpoison_page to put refcount for memory error ↵Wanpeng Li
handling Introduce put_hwpoison_page to put refcount for memory error handling. Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> Suggested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/hwpoison: fix PageHWPoison test/set raceWanpeng Li
There is a race between madvise_hwpoison path and memory_failure: CPU0 CPU1 madvise_hwpoison get_user_pages_fast PageHWPoison check (false) memory_failure TestSetPageHWPoison soft_offline_page PageHWPoison check (true) return -EBUSY (without put_page) Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> Suggested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm/hwpoison: fix failure to split thp w/ refcount heldWanpeng Li
THP pages will get a refcount in madvise_hwpoison() w/ MF_COUNT_INCREASED flag, however, the refcount is still held when fail to split THP pages. Fix it by reducing the refcount of THP pages when fail to split THP. Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-08mm: add utility for early copy from unmapped ramMark Salter
When booting an arm64 kernel w/initrd using UEFI/grub, use of mem= will likely cut off part or all of the initrd. This leaves it outside the kernel linear map which leads to failure when unpacking. The x86 code has a similar need to relocate an initrd outside of mapped memory in some cases. The current x86 code uses early_memremap() to copy the original initrd from unmapped to mapped RAM. This patchset creates a generic copy_from_early_mem() utility based on that x86 code and has arm64 and x86 share it in their respective initrd relocation code. This patch (of 3): In some early boot circumstances, it may be necessary to copy from RAM outside the kernel linear mapping to mapped RAM. The need to relocate an initrd is one example in the x86 code. This patch creates a helper function based on current x86 code. Signed-off-by: Mark Salter <msalter@redhat.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Yinghai Lu <yinghai@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>