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SubjectRe: [PATCH 0/2] memcg: improving scalability by reducing lock contention at charge/uncharge
On Fri, 2 Oct 2009 13:55:31 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> Following is test result of continuous page-fault on my 8cpu box(x86-64).
>
> A loop like this runs on all cpus in parallel for 60secs.
> ==
> while (1) {
> x = mmap(NULL, MEGA, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
>
> for (off = 0; off < MEGA; off += PAGE_SIZE)
> x[off]=0;
> munmap(x, MEGA);
> }
> ==
> please see # of page faults. I think this is good improvement.
>
>
> [Before]
> Performance counter stats for './runpause.sh' (5 runs):
>
> 474539.756944 task-clock-msecs # 7.890 CPUs ( +- 0.015% )
> 10284 context-switches # 0.000 M/sec ( +- 0.156% )
> 12 CPU-migrations # 0.000 M/sec ( +- 0.000% )
> 18425800 page-faults # 0.039 M/sec ( +- 0.107% )
> 1486296285360 cycles # 3132.080 M/sec ( +- 0.029% )
> 380334406216 instructions # 0.256 IPC ( +- 0.058% )
> 3274206662 cache-references # 6.900 M/sec ( +- 0.453% )
> 1272947699 cache-misses # 2.682 M/sec ( +- 0.118% )
>
> 60.147907341 seconds time elapsed ( +- 0.010% )
>
> [After]
> Performance counter stats for './runpause.sh' (5 runs):
>
> 474658.997489 task-clock-msecs # 7.891 CPUs ( +- 0.006% )
> 10250 context-switches # 0.000 M/sec ( +- 0.020% )
> 11 CPU-migrations # 0.000 M/sec ( +- 0.000% )
> 33177858 page-faults # 0.070 M/sec ( +- 0.152% )
> 1485264748476 cycles # 3129.120 M/sec ( +- 0.021% )
> 409847004519 instructions # 0.276 IPC ( +- 0.123% )
> 3237478723 cache-references # 6.821 M/sec ( +- 0.574% )
> 1182572827 cache-misses # 2.491 M/sec ( +- 0.179% )
>
> 60.151786309 seconds time elapsed ( +- 0.014% )
>
BTW, this is a score in root cgroup.


473811.590852 task-clock-msecs # 7.878 CPUs ( +- 0.006% )
10257 context-switches # 0.000 M/sec ( +- 0.049% )
10 CPU-migrations # 0.000 M/sec ( +- 0.000% )
36418112 page-faults # 0.077 M/sec ( +- 0.195% )
1482880352588 cycles # 3129.684 M/sec ( +- 0.011% )
410948762898 instructions # 0.277 IPC ( +- 0.123% )
3182986911 cache-references # 6.718 M/sec ( +- 0.555% )
1147144023 cache-misses # 2.421 M/sec ( +- 0.137% )


Then,
36418112 x 100 / 33177858 = 109% slower in children cgroup.

But, Hmm, this test is an extreme case.(60sec continuous page faults on all cpus.)
We may can do something more, but this score itself is not so bad. I think.
Results on more cpus are welcome. Programs I used are attached.

Thanks,
-Kame



#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <signal.h>

#define PAGE_SIZE (4096)
#define MEGA (1024 * 1024)

void sigalarm_handler(int sig)
{
}

int main(int argc, char *argv[])
{
char *x;
int off;

signal(SIGALRM, sigalarm_handler);
pause();
while (1) {
x = mmap(NULL, MEGA, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);

for (off = 0; off < MEGA; off += PAGE_SIZE)
x[off]=0;
munmap(x, MEGA);
}
}
#!/bin/sh

for i in 0 1 2 3 4 5 6 7 ;do
taskset -c $i ./pagefault &
done

pkill -ALRM pagefault
sleep 60
pkill -HUP pagefault
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