Re: [PACTH v2 0/3] Implement /proc/<pid>/totmaps

[Minchan Kim <minchan@kernel.org>]

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On Mon, Aug 22, 2016 at 09:40:52AM +0200, Michal Hocko wrote:
> On Mon 22-08-16 09:07:45, Minchan Kim wrote:
> [...]
> > #!/bin/sh
> > ./smap_test &
> > pid=$!
> > 
> > for i in $(seq 25)
> > do
> >         awk '/^Rss/{rss+=$2} /^Pss/{pss+=$2} END {}' \
> >          /proc/$pid/smaps
> > done
> > kill $pid
> > 
> > root@bbox:/home/barrios/test/smap# time ./s.sh 
> > pid:21973
> > 
> > real    0m17.812s
> > user    0m12.612s
> > sys     0m5.187s
> 
> retested on the bare metal (x86_64 - 2CPUs)
>         Command being timed: "sh s.sh"
>         User time (seconds): 0.00
>         System time (seconds): 18.08
>         Percent of CPU this job got: 98%
>         Elapsed (wall clock) time (h:mm:ss or m:ss): 0:18.29
> 
> multiple runs are quite consistent in those numbers. I am running with
> $ awk --version
> GNU Awk 4.1.3, API: 1.1 (GNU MPFR 3.1.4, GNU MP 6.1.0)
> 
> > > like a problem we are not able to address. And I would even argue that
> > > we want to address it in a generic way as much as possible.
> > 
> > Sure. What solution do you think as generic way?
> 
> either optimize seq_printf or replace it with something faster.

If it's real culprit, I agree. However, I tested your test program on
my 2 x86 machines and my friend's machine.

Ubuntu, Fedora, Arch

They have awk 4.0.1 and 4.1.3.

Result are same. Userspace speand more times I mentioned.

[root@blaptop smap_test]# time awk '/^Rss/{rss+=$2} /^Pss/{pss+=$2} END {printf "rss:%d pss:%d\n", rss, pss}' /proc/3552/smaps
rss:263484 pss:262188

real    0m0.770s
user    0m0.574s
sys     0m0.197s

I will attach my test progrma source.
I hope you guys test and repost the result because it's the key for direction
of patchset.

Thanks.

[-- Attachment #2: smap_test.c --]
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#include <sys/mman.h>

int main()
{
	unsigned long nr_vma = 0;

        while (1) {
		if (mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_SHARED|MAP_POPULATE, -1, 0) == MAP_FAILED)
			break;
		nr_vma++;
        };

        printf("pid:%d nr_vma:%lu\n", getpid(), nr_vma);
        pause();
        return 0;
}