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authorFeng Tang <feng.tang@intel.com>2020-08-06 23:23:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-07 11:33:26 -0700
commit1455083c1d70f69028df0eb92b69fd24db277e4b (patch)
tree625d1ecbadcf3fda804f0f5c3e11471383a2e086 /fs/proc
parent7bba8f0ea428f8a904c022b86e584009a2f87357 (diff)
proc/meminfo: avoid open coded reading of vm_committed_as
Patch series "make vm_committed_as_batch aware of vm overcommit policy", v6. When checking a performance change for will-it-scale scalability mmap test [1], we found very high lock contention for spinlock of percpu counter 'vm_committed_as': 94.14% 0.35% [kernel.kallsyms] [k] _raw_spin_lock_irqsave 48.21% _raw_spin_lock_irqsave;percpu_counter_add_batch;__vm_enough_memory;mmap_region;do_mmap; 45.91% _raw_spin_lock_irqsave;percpu_counter_add_batch;__do_munmap; Actually this heavy lock contention is not always necessary. The 'vm_committed_as' needs to be very precise when the strict OVERCOMMIT_NEVER policy is set, which requires a rather small batch number for the percpu counter. So keep 'batch' number unchanged for strict OVERCOMMIT_NEVER policy, and enlarge it for not-so-strict OVERCOMMIT_ALWAYS and OVERCOMMIT_GUESS policies. Benchmark with the same testcase in [1] shows 53% improvement on a 8C/16T desktop, and 2097%(20X) on a 4S/72C/144T server. And for that case, whether it shows improvements depends on if the test mmap size is bigger than the batch number computed. We tested 10+ platforms in 0day (server, desktop and laptop). If we lift it to 64X, 80%+ platforms show improvements, and for 16X lift, 1/3 of the platforms will show improvements. And generally it should help the mmap/unmap usage,as Michal Hocko mentioned: : I believe that there are non-synthetic worklaods which would benefit : from a larger batch. E.g. large in memory databases which do large : mmaps during startups from multiple threads. Note: There are some style complain from checkpatch for patch 4, as sysctl handler declaration follows the similar format of sibling functions [1] https://lore.kernel.org/lkml/20200305062138.GI5972@shao2-debian/ This patch (of 4): Use the existing vm_memory_committed() instead, which is also convenient for future change. Signed-off-by: Feng Tang <feng.tang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Qian Cai <cai@lca.pw> Cc: Kees Cook <keescook@chromium.org> Cc: Andi Kleen <andi.kleen@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Christoph Lameter <cl@linux.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: kernel test robot <rong.a.chen@intel.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/1594389708-60781-1-git-send-email-feng.tang@intel.com Link: http://lkml.kernel.org/r/1594389708-60781-2-git-send-email-feng.tang@intel.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/meminfo.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 2a4c58f70fb9..887a5532e449 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -41,7 +41,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
si_meminfo(&i);
si_swapinfo(&i);
- committed = percpu_counter_read_positive(&vm_committed_as);
+ committed = vm_memory_committed();
cached = global_node_page_state(NR_FILE_PAGES) -
total_swapcache_pages() - i.bufferram;