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

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Message-ID: <p73r6isc6ev.fsf@bingen.suse.de>
Date:	Thu, 15 Nov 2007 08:30:16 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH] NET : rt_check_expire() can take a long time, add a cond_resched()

Eric Dumazet <dada1@...mosbay.com> writes:
>
> Using a "if (need_resched())" test before calling "cond_resched();" is
> necessary to avoid spending too much time doing the resched check.

The only difference between cond_resched() and if (need_resched())
cond_resched() is one function call less and one might_sleep less. If
the might_sleep or the function call are really problems (did you
measure it? -- i doubt it somewhat) then it would be better to fix the
generic code to either inline that or supply a __cond_resched()
without might_sleep.

A cheaper change might have been to just limit the number of buckets
scanned.

-Andi
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