linux-kernel - Re: [PATCH -v2] Audit: push audit success and retcode into arch ptrace.h

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Date:	Wed, 8 Jun 2011 20:37:20 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-kernel@...r.kernel.org, tony.luck@...el.com,
	fenghua.yu@...el.com, monstr@...str.eu, ralf@...ux-mips.org,
	benh@...nel.crashing.org, paulus@...ba.org, schwidefsky@...ibm.com,
	heiko.carstens@...ibm.com, linux390@...ibm.com,
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	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [PATCH -v2] Audit: push audit success and retcode into arch
	ptrace.h

On 06/08, Eric Paris wrote:
>
> On Wed, 2011-06-08 at 18:36 +0200, Oleg Nesterov wrote:
> > And I guess, all CONFIG_AUDITSYSCALL code in entry.S is only needed to
> > microoptimize the case when TIF_SYSCALL_AUDIT is the only reason for the
> > slow path. I wonder if it really makes the measureble difference...
>
> All I know is what Roland put in the changelog:
>
> Avoiding the iret return path when syscall audit is enabled helps
> performance a lot.
>
> I believe this was a result of Fedora starting auditd by default and
> then Linus bitching about how slow a null syscall in a tight loop was.
> It was an optimization for a microbenchmark.  How much it affects things
> on a real syscall that does real work is probably going to be determined
> by how much work is done in the syscall.

and probably by how much work is done in audit_syscall_entry/exit.

OK. Thanks a lot Eric for your explanations.

Oleg.

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