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Message-ID: <20120627123455.GA32171@altlinux.org>
Date: Wed, 27 Jun 2012 16:34:55 +0400
From: "Dmitry V. Levin" <ldv@...linux.org>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Doug Ledford <dledford@...hat.com>,
Al Viro <viro@...iv.linux.org.uk>,
Serge Hallyn <serge.hallyn@...onical.com>,
linux-kernel@...r.kernel.org,
"Kirill A. Shutemov" <kirill@...temov.name>
Subject: Re: [RFC, PATCH] CLONE_NEWIPC and exit_group()
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
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