Message-ID: <4640906B.2020301@redhat.com>
Date: Tue, 08 May 2007 10:59:55 -0400
From: Rik van Riel <riel@redhat.com>
Organization: Red Hat, Inc
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To: Nick Piggin <nickpiggin@yahoo.com.au>
CC: Ulrich Drepper <drepper@redhat.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       linux-mm <linux-mm@kvack.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Jakub Jelinek <jakub@redhat.com>
Subject: Re: [PATCH] MM: implement MADV_FREE lazy freeing of anonymous memory
References: <4632D0EF.9050701@redhat.com> <463B108C.10602@yahoo.com.au> <463B598B.80200@redhat.com> <463BC62C.3060605@yahoo.com.au> <463E5A00.6070708@redhat.com> <464014B0.7060308@yahoo.com.au>
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Nick Piggin wrote:

> We have percpu and cache affine page allocators, so when
> userspace just frees a page, it is likely to be cache hot, so
> we want to free it up so it can be reused by this CPU ASAP.
> Likewise, when we newly allocate a page, we want it to be one
> that is cache hot on this CPU.

Actually, isn't the clear page function capable of doing
some magic, when it writes all zeroes into the page, that
causes the zeroes to just live in CPU cache without the old
data ever being loaded from RAM?

That would sure be faster than touching RAM.  Not sure if
we use/trigger that kind of magic, though :)

-- 
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is.  Each group
calls the other unpatriotic.
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