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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2009-12-15 16:47:03 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-16 07:20:07 -0800
commit569b846df54ffb2827b83ce3244c5f032394cba4 (patch)
tree77c5d373a5edf97710fab8777912971b99e84828 /mm/truncate.c
parentcd9b45b78a61e8df250e69385c74e729e5b66abf (diff)
memcg: coalesce uncharge during unmap/truncate
In massive parallel enviroment, res_counter can be a performance bottleneck. One strong techinque to reduce lock contention is reducing calls by coalescing some amount of calls into one. Considering charge/uncharge chatacteristic, - charge is done one by one via demand-paging. - uncharge is done by - in chunk at munmap, truncate, exit, execve... - one by one via vmscan/paging. It seems we have a chance to coalesce uncharges for improving scalability at unmap/truncation. This patch is a for coalescing uncharge. For avoiding scattering memcg's structure to functions under /mm, this patch adds memcg batch uncharge information to the task. A reason for per-task batching is for making use of caller's context information. We do batched uncharge (deleyed uncharge) when truncation/unmap occurs but do direct uncharge when uncharge is called by memory reclaim (vmscan.c). The degree of coalescing depends on callers - at invalidate/trucate... pagevec size - at unmap ....ZAP_BLOCK_SIZE (memory itself will be freed in this degree.) Then, we'll not coalescing too much. On x86-64 8cpu server, I tested overheads of memcg at page fault by running a program which does map/fault/unmap in a loop. Running a task per a cpu by taskset and see sum of the number of page faults in 60secs. [without memcg config] 40156968 page-faults # 0.085 M/sec ( +- 0.046% ) 27.67 cache-miss/faults [root cgroup] 36659599 page-faults # 0.077 M/sec ( +- 0.247% ) 31.58 miss/faults [in a child cgroup] 18444157 page-faults # 0.039 M/sec ( +- 0.133% ) 69.96 miss/faults [child with this patch] 27133719 page-faults # 0.057 M/sec ( +- 0.155% ) 47.16 miss/faults We can see some amounts of improvement. (root cgroup doesn't affected by this patch) Another patch for "charge" will follow this and above will be improved more. Changelog(since 2009/10/02): - renamed filed of memcg_batch (as pages to bytes, memsw to memsw_bytes) - some clean up and commentary/description updates. - added initialize code to copy_process(). (possible bug fix) Changelog(old): - fixed !CONFIG_MEM_CGROUP case. - rebased onto the latest mmotm + softlimit fix patches. - unified patch for callers - added commetns. - make ->do_batch as bool. - removed css_get() at el. We don't need it. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/truncate.c')
-rw-r--r--mm/truncate.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/mm/truncate.c b/mm/truncate.c
index 2c147a7e5f2c..342deee22684 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -272,6 +272,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
pagevec_release(&pvec);
break;
}
+ mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
@@ -286,6 +287,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
unlock_page(page);
}
pagevec_release(&pvec);
+ mem_cgroup_uncharge_end();
}
}
EXPORT_SYMBOL(truncate_inode_pages_range);
@@ -327,6 +329,7 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
pagevec_init(&pvec, 0);
while (next <= end &&
pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
+ mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
pgoff_t index;
@@ -354,6 +357,7 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
break;
}
pagevec_release(&pvec);
+ mem_cgroup_uncharge_end();
cond_resched();
}
return ret;
@@ -428,6 +432,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
while (next <= end && !wrapped &&
pagevec_lookup(&pvec, mapping, next,
min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
+ mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
pgoff_t page_index;
@@ -477,6 +482,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
unlock_page(page);
}
pagevec_release(&pvec);
+ mem_cgroup_uncharge_end();
cond_resched();
}
return ret;

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