netdev - Re: [PATCH] NET : rt_check_expire() can take a long time, add a cond

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Message-Id: <20071114.161308.66154917.davem@davemloft.net>
Date:	Wed, 14 Nov 2007 16:13:08 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	dada1@...mosbay.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] NET : rt_check_expire() can take a long time, add a
 cond_resched()

From: Eric Dumazet <dada1@...mosbay.com>
Date: Wed, 14 Nov 2007 22:34:13 +0100

> On commit 39c90ece7565f5c47110c2fa77409d7a9478bd5b we converted 
> rt_check_expire() from softirq to workqueue, allowing the function to perform 
> all work it was supposed to do.
> 
> When the IP route cache is big, rt_check_expire() can take a long time to run.
> (default settings : 20% of the hash table is scanned at each invocation)
> 
> Adding cond_resched() helps giving cpu to higher priority tasks if necessary.
> 
> Using a "if (need_resched())" test before calling "cond_resched();" is 
> necessary to avoid spending too much time doing the resched check.
> (My tests gave a time reduction from 88 ms to 25 ms per rt_check_expire() run 
> on my i686 test machine)
> 
> Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

Patch applied, thanks!
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