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

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Message-Id: <E1ItPUJ-0005Ue-00@gondolin.me.apana.org.au>
Date:	Sat, 17 Nov 2007 23:21:39 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	andi@...stfloor.org (Andi Kleen)
Cc:	arjan@...radead.org, dada1@...mosbay.com,
	linux-kernel@...r.kernel.org, davem@...emloft.net,
	netdev@...t.kernel.org, mingo@...e.hu
Subject: Re: [NET]: rt_check_expire() can take a long time, add a cond_resched()

Andi Kleen <andi@...stfloor.org> wrote:
>
>>> > With the extra check (and *much* less function calls), each run
>>> > takes 25ms
> 
> ms?!? The numbers sound wrong. Wrong unit? 

That's quite possible with a huge routing cache.  I think that's
the reason Eric is doing this in the first place.

>> however... this is likely a good argument for making cond_resched() as a
>> whole a #define (or inline) that does this test and then calls the out
>> of line code (which then doesn't need to retest, so it avoids the
>> double test)...
> 
> Disadvantage would be that might_sleep would be commonly skipped then
> (unless you actually need to reschedule) 
> But perhaps that's not a big issue.

On a related note, would it be possible for cond_resched() to
be compiled out completely if we're doing real preemption as
opposed to voluntary preemption?

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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