linux-kernel - Re: [patch] x86, mm: pass in 'total' to __copy_from_user

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Message-ID: <8763iu309p.fsf@basil.nowhere.org>
Date:	Sat, 28 Feb 2009 19:05:22 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Salman Qazi <sqazi@...gle.com>, davem@...emloft.net,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [patch] x86, mm: pass in 'total' to __copy_from_user_*nocache()

Linus Torvalds <torvalds@...ux-foundation.org> writes:

> That's almost unacceptable in the long run. With a 8MB L3 cache - and a 
> compile sequence, do we really want to go out to memory to write the .S 
> file, and then have the assembler go out to memory to read it back? For 

One possible way would be to make the threshold dependent on the LLC
cache size, so that let's say an Atom still prefers to not pollute
its caches.  But I agree with you that it's probably better to 
just drop the nocache copies completely.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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