From db16d5ec1f87f17511599bc77857dd1662b5a22f Mon Sep 17 00:00:00 2001 From: Greg Thelen Date: Thu, 13 Jan 2011 15:47:35 -0800 Subject: [PATCH] memcg: add page_cgroup flags for dirty page tracking This patchset provides the ability for each cgroup to have independent dirty page limits. Limiting dirty memory is like fixing the max amount of dirty (hard to reclaim) page cache used by a cgroup. So, in case of multiple cgroup writers, they will not be able to consume more than their designated share of dirty pages and will be forced to perform write-out if they cross that limit. The patches are based on a series proposed by Andrea Righi in Mar 2010. Overview: - Add page_cgroup flags to record when pages are dirty, in writeback, or nfs unstable. - Extend mem_cgroup to record the total number of pages in each of the interesting dirty states (dirty, writeback, unstable_nfs). - Add dirty parameters similar to the system-wide /proc/sys/vm/dirty_* limits to mem_cgroup. The mem_cgroup dirty parameters are accessible via cgroupfs control files. - Consider both system and per-memcg dirty limits in page writeback when deciding to queue background writeback or block for foreground writeback. Known shortcomings: - When a cgroup dirty limit is exceeded, then bdi writeback is employed to writeback dirty inodes. Bdi writeback considers inodes from any cgroup, not just inodes contributing dirty pages to the cgroup exceeding its limit. - When memory.use_hierarchy is set, then dirty limits are disabled. This is a implementation detail. An enhanced implementation is needed to check the chain of parents to ensure that no dirty limit is exceeded. Performance data: - A page fault microbenchmark workload was used to measure performance, which can be called in read or write mode: f = open(foo. $cpu) truncate(f, 4096) alarm(60) while (1) { p = mmap(f, 4096) if (write) *p = 1 else x = *p munmap(p) } - The workload was called for several points in the patch series in different modes: - s_read is a single threaded reader - s_write is a single threaded writer - p_read is a 16 thread reader, each operating on a different file - p_write is a 16 thread writer, each operating on a different file - Measurements were collected on a 16 core non-numa system using "perf stat --repeat 3". The -a option was used for parallel (p_*) runs. - All numbers are page fault rate (M/sec). Higher is better. - To compare the performance of a kernel without non-memcg compare the first and last rows, neither has memcg configured. The first row does not include any of these memcg patches. - To compare the performance of using memcg dirty limits, compare the baseline (2nd row titled "w/ memcg") with the the code and memcg enabled (2nd to last row titled "all patches"). root_cgroup child_cgroup s_read s_write p_read p_write s_read s_write p_read p_write mmotm w/o memcg 0.428 0.390 0.429 0.388 mmotm w/ memcg 0.411 0.378 0.391 0.362 0.412 0.377 0.385 0.363 all patches 0.384 0.360 0.370 0.348 0.381 0.363 0.368 0.347 all patches 0.431 0.402 0.427 0.395 w/o memcg This patch: Add additional flags to page_cgroup to track dirty pages within a mem_cgroup. Signed-off-by: KAMEZAWA Hiroyuki Signed-off-by: Andrea Righi Signed-off-by: Greg Thelen Acked-by: Daisuke Nishimura Cc: Balbir Singh Cc: Minchan Kim Cc: Wu Fengguang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/page_cgroup.h | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h index b02195dfc1b0..fdb5a92b5ac7 100644 --- a/include/linux/page_cgroup.h +++ b/include/linux/page_cgroup.h @@ -40,6 +40,9 @@ enum { PCG_USED, /* this object is in use. */ PCG_ACCT_LRU, /* page has been accounted for */ PCG_FILE_MAPPED, /* page is accounted as "mapped" */ + PCG_FILE_DIRTY, /* page is dirty */ + PCG_FILE_WRITEBACK, /* page is under writeback */ + PCG_FILE_UNSTABLE_NFS, /* page is NFS unstable */ PCG_MIGRATION, /* under page migration */ }; @@ -59,6 +62,10 @@ static inline void ClearPageCgroup##uname(struct page_cgroup *pc) \ static inline int TestClearPageCgroup##uname(struct page_cgroup *pc) \ { return test_and_clear_bit(PCG_##lname, &pc->flags); } +#define TESTSETPCGFLAG(uname, lname) \ +static inline int TestSetPageCgroup##uname(struct page_cgroup *pc) \ + { return test_and_set_bit(PCG_##lname, &pc->flags); } + /* Cache flag is set only once (at allocation) */ TESTPCGFLAG(Cache, CACHE) CLEARPCGFLAG(Cache, CACHE) @@ -78,6 +85,22 @@ SETPCGFLAG(FileMapped, FILE_MAPPED) CLEARPCGFLAG(FileMapped, FILE_MAPPED) TESTPCGFLAG(FileMapped, FILE_MAPPED) +SETPCGFLAG(FileDirty, FILE_DIRTY) +CLEARPCGFLAG(FileDirty, FILE_DIRTY) +TESTPCGFLAG(FileDirty, FILE_DIRTY) +TESTCLEARPCGFLAG(FileDirty, FILE_DIRTY) +TESTSETPCGFLAG(FileDirty, FILE_DIRTY) + +SETPCGFLAG(FileWriteback, FILE_WRITEBACK) +CLEARPCGFLAG(FileWriteback, FILE_WRITEBACK) +TESTPCGFLAG(FileWriteback, FILE_WRITEBACK) + +SETPCGFLAG(FileUnstableNFS, FILE_UNSTABLE_NFS) +CLEARPCGFLAG(FileUnstableNFS, FILE_UNSTABLE_NFS) +TESTPCGFLAG(FileUnstableNFS, FILE_UNSTABLE_NFS) +TESTCLEARPCGFLAG(FileUnstableNFS, FILE_UNSTABLE_NFS) +TESTSETPCGFLAG(FileUnstableNFS, FILE_UNSTABLE_NFS) + SETPCGFLAG(Migration, MIGRATION) CLEARPCGFLAG(Migration, MIGRATION) TESTPCGFLAG(Migration, MIGRATION) -- 2.30.2