Re: [RFC, PATCH] CLONE_NEWIPC and exit_group()
From: Kirill A. Shutemov
Date: Tue Jun 26 2012 - 13:44:08 EST
On Tue, Jun 26, 2012 at 05:04:57PM +0000, Serge E. Hallyn wrote:
> Quoting Kirill A. Shutemov (kirill.shutemov@xxxxxxxxxxxxxxx):
> > Hi,
> >
> > 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?
>
> Hi,
>
> sorry, I don't seem to have the thread handy for contest. What is the
> point of this? The work being moved was not being done under lock,
> so what is this meant to gain?
It's basically addition to this patch (tested with the patch applied):
http://thread.gmane.org/gmane.linux.kernel.cifs/6347/focus=23929
Some context: Dmitry has workload which run a lot of short-living tasks in
sandboxed environment. He noticed that exit_group() syscall of the last
process in IPC namespace is a bottleneck.
The bottleneck was mainly due rcu_barrier() in kern_umount(). It's fixed
by patch in the link (Andrew took it in -mm).
But probably having kern_umount() in exit_group() code path is not a good
idea from scalability point of view?..
--
Kirill A. Shutemov
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