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From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] tg3 : avoid an expensive divide
Date: Wed, 07 Feb 2007 01:45:14 -0800 (PST)
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From: Andi Kleen <ak@suse.de>
Date: 07 Feb 2007 10:54:49 +0100

> Probably Eric compiled with the now default CONFIG_CC_OPTIMIZE_FOR_SIZE/-Os.
> With that gcc decides to use the shorter hardware divide instruction, even
> though it is significantly slower than an expanded optimized sequence
> for constant dividend.
> 
> We've seen this in a few other cases while during performance regression
> testing between kernels that still used -O2 vs the newer -Os.
> 
> No good solution found unfortunately.

Thanks for the explanation, that makes a lot of sense.