Re: [RFC, PATCH] CLONE_NEWIPC and exit_group()

["Dmitry V. Levin" <ldv@altlinux.org>]

Hi,

On Tue, Jun 26, 2012 at 03:04:26PM +0300, Kirill A. Shutemov wrote:
> Patch to move kern_unmount() out of exit_group() code path is below.
> Dmitry, could you check if it's beneficial for your use-case?

I've benchmarked a slightly modified test which is closer to our use-case
(child processes are forked sequentially):

#define _GNU_SOURCE
#include <unistd.h>
#include <sched.h>
#include <stdlib.h>
#include <sys/wait.h>

int
main(void)
{
	int i;
	for (i = 0; i < 1024; i++) {
		if (fork()) {
			wait(NULL);
			continue;
		}
		unshare(CLONE_NEWIPC);
		exit(0);
	}
	return 0;
}

On 3.4.4 with rcu_barrier patch:
0.09user 0.00system 0:32.77elapsed 0%CPU (0avgtext+0avgdata 1472maxresident)k
0inputs+0outputs (0major+38017minor)pagefaults 0swaps

On 3.4.4 with rcu_barrier patch and your new patch:
0.00user 0.06system 0:32.77elapsed 0%CPU (0avgtext+0avgdata 1472maxresident)k
0inputs+0outputs (0major+38017minor)pagefaults 0swaps

So there is a clear difference in accounting (user vs system) but no
noticeable difference in the real time.


-- 
ldv