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* [PATCH 0/3] make vm_committed_as_batch aware of vm overcommit policy
@ 2020-05-08  7:25 Feng Tang
  2020-05-08  7:25 ` [PATCH 1/3] proc/meminfo: avoid open coded reading of vm_committed_as Feng Tang
                   ` (3 more replies)
  0 siblings, 4 replies; 34+ messages in thread
From: Feng Tang @ 2020-05-08  7:25 UTC (permalink / raw)
  To: Andrew Morton, Michal Hocko, Johannes Weiner, Matthew Wilcox,
	Mel Gorman, Kees Cook, Luis Chamberlain, Iurii Zaikin,
	andi.kleen, tim.c.chen, dave.hansen, ying.huang, linux-mm,
	linux-kernel
  Cc: Feng Tang

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 lift the batch number to 16X for OVERCOMMIT_ALWAYS and
OVERCOMMIT_GUESS policies, and add a sysctl handler to adjust it
when the policy is reconfigured.

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 no change
for some platforms, due to the test mmap size of the case is bigger
than the batch number computed, though the patch will help mmap/munmap
generally.

[1] https://lkml.org/lkml/2020/3/5/57

There are some style complain from checkpatch for patch 3, as it
follows the similar format of sibling functions

patch1: a cleanup for /proc/meminfo
patch2: a preparation patch which also improve the accuracy of
        vm_memory_committed
patch3: the main change

Please help to review, thanks!

- Feng

----------------------------------------------------------------
Changelog:
  v2:
     * add the sysctl handler to cover runtime overcommit policy
       change, as suggested by Andres Morton 
     * address the accuracy concern of vm_memory_committed()
       from Andi Kleen 

Feng Tang (3):
  proc/meminfo: avoid open coded reading of vm_committed_as
  mm/util.c: make vm_memory_committed() more accurate
  mm: adjust vm_committed_as_batch according to vm overcommit policy

 fs/proc/meminfo.c    |  2 +-
 include/linux/mm.h   |  2 ++
 include/linux/mman.h |  4 ++++
 kernel/sysctl.c      |  2 +-
 mm/mm_init.c         | 19 +++++++++++++++----
 mm/util.c            | 15 ++++++++++++++-
 6 files changed, 37 insertions(+), 7 deletions(-)

-- 
2.7.4


^ permalink raw reply	[flat|nested] 34+ messages in thread

end of thread, other threads:[~2020-05-29 16:04 UTC | newest]

Thread overview: 34+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-08  7:25 [PATCH 0/3] make vm_committed_as_batch aware of vm overcommit policy Feng Tang
2020-05-08  7:25 ` [PATCH 1/3] proc/meminfo: avoid open coded reading of vm_committed_as Feng Tang
2020-05-15  7:22   ` Michal Hocko
2020-05-08  7:25 ` [PATCH 2/3] mm/util.c: make vm_memory_committed() more accurate Feng Tang
2020-05-15  7:23   ` Michal Hocko
2020-05-15  8:11     ` Feng Tang
2020-05-15  9:04       ` Michal Hocko
2020-05-15 13:01         ` Feng Tang
2020-05-08  7:25 ` [PATCH 3/3] mm: adjust vm_committed_as_batch according to vm overcommit policy Feng Tang
2020-05-08 11:24   ` Matthew Wilcox
2020-05-08 12:33     ` Feng Tang
2020-05-15  7:41   ` Michal Hocko
2020-05-15  8:02     ` Feng Tang
2020-05-15  9:08       ` Michal Hocko
2020-05-15 11:26         ` Feng Tang
2020-05-15  7:44   ` Michal Hocko
2020-05-15  8:38     ` Feng Tang
2020-05-21 21:27 ` [PATCH 0/3] make vm_committed_as_batch aware of " Qian Cai
2020-05-26 18:14   ` Qian Cai
2020-05-27  1:14     ` Andi Kleen
2020-05-27  1:43       ` Feng Tang
2020-05-27  1:46     ` Feng Tang
2020-05-27  2:25       ` Qian Cai
2020-05-27 10:46         ` Feng Tang
2020-05-27 12:05           ` Qian Cai
2020-05-27 13:33             ` Feng Tang
2020-05-27 15:42               ` Qian Cai
2020-05-28 14:18           ` Qian Cai
2020-05-28 15:10             ` Feng Tang
2020-05-28 15:21               ` Kleen, Andi
2020-05-29 15:43                 ` Feng Tang
2020-05-29 15:50                   ` Andi Kleen
2020-05-29 16:04                     ` Feng Tang
2020-05-28 15:48               ` Michal Hocko

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