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SubjectRe: [PATCH 00/14] per memcg lru_lock
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Hi Alex,

On 8/20/19 5:48 AM, Alex Shi wrote:
> In some data center, containers are used widely to deploy different kind
> of services, then multiple memcgs share per node pgdat->lru_lock which
> cause heavy lock contentions when doing lru operation.
>
> On my 2 socket * 6 cores E5-2630 platform, 24 containers run aim9
> simultaneously with mmtests' config:
> # AIM9
> export AIM9_TESTTIME=180
> export AIM9_TESTLIST=page_test,brk_test
>
> perf lock report show much contentions on lru_lock in 20 second snapshot:
> Name acquired contended avg wait (ns) total wait (ns) max wait (ns) min wait (ns)
> &(ptlock_ptr(pag... 22 0 0 0 0 0
> ...
> &(&pgdat->lru_lo... 9 7 12728 89096 26656 1597

This is system-wide right, not per container? Even per container, 89 usec isn't much contention over 20 seconds. You may want to give this a try:

https://git.kernel.org/pub/scm/linux/kernel/git/wfg/vm-scalability.git/tree/case-lru-file-readtwice

It's also synthetic but it stresses lru_lock more than just anon alloc/free. It hits the page activate path, which is where we see this lock in our database, and if enough memory is configured lru_lock also gets stressed during reclaim, similar to [1].

It'd be better though, as Michal suggests, to use the real workload that's causing problems. Where are you seeing contention?

> With this patch series, lruvec->lru_lock show no contentions
> &(&lruvec->lru_l... 8 0 0 0 0 0
>
> and aim9 page_test/brk_test performance increased 5%~50%.

Where does the 50% number come in? The numbers below seem to only show ~4% boost.

> BTW, Detailed results in aim9-pft.compare.log if needed,
> All containers data are increased and pretty steady.
>
> $for i in Max Min Hmean Stddev CoeffVar BHmean-50 BHmean-95 BHmean-99; do echo "========= $i page_test ============"; cat aim9-pft.compare.log | grep "^$i.*page_test" | awk 'BEGIN {a=b=0;} { a+=$3; b+=$6 } END { print "5.3-rc4 " a/24; print "5.3-rc4+lru_lock " b/24}' ; done
> ========= Max page_test ============
> 5.3-rc4 34729.6
> 5.3-rc4+lru_lock 36128.3
> ========= Min page_test ============
> 5.3-rc4 33644.2
> 5.3-rc4+lru_lock 35349.7
> ========= Hmean page_test ============
> 5.3-rc4 34355.4
> 5.3-rc4+lru_lock 35810.9
> ========= Stddev page_test ============
> 5.3-rc4 319.757
> 5.3-rc4+lru_lock 223.324
> ========= CoeffVar page_test ============
> 5.3-rc4 0.93125
> 5.3-rc4+lru_lock 0.623333
> ========= BHmean-50 page_test ============
> 5.3-rc4 34579.2
> 5.3-rc4+lru_lock 35977.1
> ========= BHmean-95 page_test ============
> 5.3-rc4 34421.7
> 5.3-rc4+lru_lock 35853.6
> ========= BHmean-99 page_test ============
> 5.3-rc4 34421.7
> 5.3-rc4+lru_lock 35853.6
>
> $for i in Max Min Hmean Stddev CoeffVar BHmean-50 BHmean-95 BHmean-99; do echo "========= $i brk_test ============"; cat aim9-pft.compare.log | grep "^$i.*brk_test" | awk 'BEGIN {a=b=0;} { a+=$3; b+=$6 } END { print "5.3-rc4 " a/24; print "5.3-rc4+lru_lock " b/24}' ; done
> ========= Max brk_test ============
> 5.3-rc4 96647.7
> 5.3-rc4+lru_lock 98960.3
> ========= Min brk_test ============
> 5.3-rc4 91800.8
> 5.3-rc4+lru_lock 96817.6
> ========= Hmean brk_test ============
> 5.3-rc4 95470
> 5.3-rc4+lru_lock 97769.6
> ========= Stddev brk_test ============
> 5.3-rc4 1253.52
> 5.3-rc4+lru_lock 596.593
> ========= CoeffVar brk_test ============
> 5.3-rc4 1.31375
> 5.3-rc4+lru_lock 0.609583
> ========= BHmean-50 brk_test ============
> 5.3-rc4 96141.4
> 5.3-rc4+lru_lock 98194
> ========= BHmean-95 brk_test ============
> 5.3-rc4 95818.5
> 5.3-rc4+lru_lock 97857.2
> ========= BHmean-99 brk_test ============
> 5.3-rc4 95818.5
> 5.3-rc4+lru_lock 97857.2

[1] https://lore.kernel.org/linux-mm/CABdVr8R2y9B+2zzSAT_Ve=BQCa+F+E9_kVH+C28DGpkeQitiog@mail.gmail.com/

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