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

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Message-Id: <20071117.162743.93964350.davem@davemloft.net>
Date:	Sat, 17 Nov 2007 16:27:43 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	andi@...stfloor.org
Cc:	dada1@...mosbay.com, netdev@...r.kernel.org
Subject: Re: [PATCH] NET : rt_check_expire() can take a long time, add a
 cond_resched()

From: Andi Kleen <andi@...stfloor.org>
Date: Sat, 17 Nov 2007 22:46:40 +0100

> > The 25.000.000 ns and 88.000.000 ns numbers where on an empty table, but 
> > large (16 MB of memory)
> 
> This would mean that cond_resched() needs ~4x as much time as checking
> an empty bucket. I find that somewhat hard to believe.

Based upon Arjan's analysis of the stall created by the
cond_resched() assembler, this doesn't surprise me.

I also don't believe Eric would make up such numbers or
measure them carelessly and then present them as fact.
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