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Subject: Re: clear_user_highpage()
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
In-Reply-To: <Pine.LNX.4.58.0408111654440.1839@ppc970.osdl.org>
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Date: Thu, 12 Aug 2004 10:06:37 +1000
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To: Linus Torvalds <torvalds@osdl.org>
Cc: "David S. Miller" <davem@redhat.com>, Linux Arch list <linux-arch@vger.kernel.org>
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> You didn't read my message. If it doesn't crap on the caches when you do 
> the stores, it _will_ crap on the bus both when you do the stores _and_ 
> when you actually read the page.
> 
> In other words, you will have taken _more_ of a hit later on. It's just 
> that it won't be a nice profile hit, it will be a nasty "everything runs 
> slower later".
> 
> Caches work best when you have good temporal locality. You are removing 
> that locality, and thus you are making your caches _less_ efficient.
> 
> That's a very _fundamental_ argument. 

Ok, that may be why it was removed from ppc then, I should ask Paul.

Ben.