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Message-ID: <20070607195151.GA30899@elte.hu>
Date: Thu, 7 Jun 2007 21:51:51 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Stephen Smalley <sds@...ho.nsa.gov>
Cc: linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
James Carter <jwcart2@...ho.nsa.gov>,
Paul Moore <paul.moore@...com>,
James Morris <jmorris@...ei.org>
Subject: Re: [bug] very high non-preempt latency in
context_struct_compute_av()
* Stephen Smalley <sds@...ho.nsa.gov> wrote:
> Can you try the patch below to see whether it helps?
>
> In security_get_user_sids, move the transition permission checks
> outside of the section holding the policy rdlock, and use the AVC to
> perform the checks, calling cond_resched after each one. These
> changes should allow preemption between the individual checks and
> enable caching of the results. It may however increase the overall
> time spent in the function in some cases, particularly in the cache
> miss case.
>
> The long term fix will be to take much of this logic to userspace by
> exporting additional state via selinuxfs, and ultimately deprecating
> and eliminating this interface from the kernel.
>
> Signed-off-by: Stephen Smalley <sds@...ho.nsa.gov>
i have just tried your patch and it completely solves the issue! Without
the patch, a simple script that keeps logging in on a box:
while :; do ssh testbox true; done
would cause glxgears to get into a very jerky motion due to the
latencies. With the patch it's 100%, totally smooth! Thanks!
Tested-by: Ingo Molnar <mingo@...e.hu>
Ingo
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