Re: [RFC][PATCH 0/4][mmotm] memcg: reduce lock contention v3

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Thu, 10 Sep 2009 02:00:42 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-09-09 17:39:03]:
> 
> > This patch series is for reducing memcg's lock contention on res_counter, v3.
> > (sending today just for reporting current status in my stack.)
> > 
> > It's reported that memcg's res_counter can cause heavy false sharing / lock
> > conention and scalability is not good. This is for relaxing that.
> > No terrible bugs are found, I'll maintain/update this until the end of next
> > merge window. Tests on big-smp and new-good-idea are welcome.
> > 
> > This patch is on to mmotm+Nishimura's fix + Hugh's get_user_pages() patch.
> > But can be applied directly against mmotm, I think.
> > 
> > numbers:
> > 
> > I used 8cpu x86-64 box and run make -j 12 kernel.
> > Before make, make clean and drop_caches.
> >
> 
> Kamezawa-San
> 
> I was able to test on a 24 way using my parallel page fault test
> program and here is what I see
> 
thank you.

>  Performance counter stats for '/home/balbir/parallel_pagefault' (3
> runs):
> 
>  7191673.834385  task-clock-msecs         #     23.953 CPUs    ( +- 0.001% )
>          427765  context-switches         #      0.000 M/sec   ( +- 0.106% )
>             234  CPU-migrations           #      0.000 M/sec   ( +- 20.851% )
>        87975343  page-faults              #      0.012 M/sec   ( +- 0.347% )
>   5962193345280  cycles                   #    829.041 M/sec   ( +- 0.012% )
>   1009132401195  instructions             #      0.169 IPC     ( +- 0.059% )
>     10068652670  cache-references         #      1.400 M/sec   ( +- 2.581% )
>      2053688394  cache-misses             #      0.286 M/sec   ( +- 0.481% )
> 
>   300.238748326  seconds time elapsed   ( +-   0.001% )
> 
> Without the patch I saw
> 
>  Performance counter stats for '/home/balbir/parallel_pagefault' (3
> runs):
> 
>  7198364.596593  task-clock-msecs         #     23.959 CPUs    ( +- 0.004% )
>          425104  context-switches         #      0.000 M/sec   ( +- 0.244% )
>             157  CPU-migrations           #      0.000 M/sec   ( +- 13.291% )
>        28964117  page-faults              #      0.004 M/sec   ( +- 0.106% )
>   5786854402292  cycles                   #    803.912 M/sec   ( +- 0.013% )
>    835828892399  instructions             #      0.144 IPC     ( +- 0.073% )
>      6240606753  cache-references         #      0.867 M/sec   ( +- 1.058% )
>      2068445332  cache-misses             #      0.287 M/sec   ( +- 1.844% )
> 
>   300.443366784  seconds time elapsed   ( +-   0.005% )
> 
> 
> This does look like a very good improvement.
> 
Seems good.
BTW, why the number of page-faults after patch is 3 times bigger than
one before patch ? The difference in the number of instructions  meets it ?

THanks,
-Kame




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