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Date: Fri, 13 Jul 2012 14:08:06 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        Pavel Emelyanov <xemul@openvz.org>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Doug Ledford <dledford@redhat.com>, linux-kernel@vger.kernel.org,
        containers@lists.linux-foundation.org
Subject: Re: [PATCH] ns: move free_nsproxy() out of do_exit() path
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On Fri, 13 Jul 2012 14:48:08 +0300
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> wrote:

> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> 
> free_nsproxy() is too heavy to be on exit path. Let's free namespaces
> asynchronously to not block exit_group() syscall.

Please be specific, and complete.

Why is it "too heavy"?  Where is the time being spent?  Is it spent in
D state or is it spent burning CPU cycles?  Does the patch simply
offload the work into kernel threads, providing no net gain?

> The patch also fixes bug with free namespace without synchronize_rcu() through
> put_nsproxy().

I just don't understand this description.  Please send a new one which
includes all details about the bug, including a description of
the user-visible effects of the bug.