summaryrefslogtreecommitdiff
path: root/mm/page_alloc.c
diff options
context:
space:
mode:
authorChristoph Lameter <clameter@sgi.com>2006-07-03 00:24:13 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-07-03 15:26:59 -0700
commit9614634fe6a138fd8ae044950700d2af8d203f97 (patch)
tree9b020c1d36d8625f4048c057058efb2e17c81973 /mm/page_alloc.c
parentcb6358eb69d9854f65f2979c0ce9280eee041828 (diff)
[PATCH] ZVC/zone_reclaim: Leave 1% of unmapped pagecache pages for file I/O
It turns out that it is advantageous to leave a small portion of unmapped file backed pages if all of a zone's pages (or almost all pages) are allocated and so the page allocator has to go off-node. This allows recently used file I/O buffers to stay on the node and reduces the times that zone reclaim is invoked if file I/O occurs when we run out of memory in a zone. The problem is that zone reclaim runs too frequently when the page cache is used for file I/O (read write and therefore unmapped pages!) alone and we have almost all pages of the zone allocated. Zone reclaim may remove 32 unmapped pages. File I/O will use these pages for the next read/write requests and the unmapped pages increase. After the zone has filled up again zone reclaim will remove it again after only 32 pages. This cycle is too inefficient and there are potentially too many zone reclaim cycles. With the 1% boundary we may still remove all unmapped pages for file I/O in zone reclaim pass. However. it will take a large number of read and writes to get back to 1% again where we trigger zone reclaim again. The zone reclaim 2.6.16/17 does not show this behavior because we have a 30 second timeout. [akpm@osdl.org: rename the /proc file and the variable] Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3e792a583f3b..54a4f5375bba 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2005,6 +2005,10 @@ static void __meminit free_area_init_core(struct pglist_data *pgdat,
zone->spanned_pages = size;
zone->present_pages = realsize;
+#ifdef CONFIG_NUMA
+ zone->min_unmapped_ratio = (realsize*sysctl_min_unmapped_ratio)
+ / 100;
+#endif
zone->name = zone_names[j];
spin_lock_init(&zone->lock);
spin_lock_init(&zone->lru_lock);
@@ -2298,6 +2302,24 @@ int min_free_kbytes_sysctl_handler(ctl_table *table, int write,
return 0;
}
+#ifdef CONFIG_NUMA
+int sysctl_min_unmapped_ratio_sysctl_handler(ctl_table *table, int write,
+ struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
+{
+ struct zone *zone;
+ int rc;
+
+ rc = proc_dointvec_minmax(table, write, file, buffer, length, ppos);
+ if (rc)
+ return rc;
+
+ for_each_zone(zone)
+ zone->min_unmapped_ratio = (zone->present_pages *
+ sysctl_min_unmapped_ratio) / 100;
+ return 0;
+}
+#endif
+
/*
* lowmem_reserve_ratio_sysctl_handler - just a wrapper around
* proc_dointvec() so that we can call setup_per_zone_lowmem_reserve()