From: David Miller <davem@davemloft.net>
To: torvalds@osdl.org
Cc: ralf@linux-mips.org, nickpiggin@yahoo.com.au, akpm@osdl.org,
linux-kernel@vger.kernel.org, anemo@mba.ocn.ne.jp,
linux-arch@vger.kernel.org, schwidefsky@de.ibm.com,
James.Bottomley@SteelEye.com
Subject: Re: [PATCH 1/3] Fix COW D-cache aliasing on fork
Date: Fri, 20 Oct 2006 15:22:47 -0700 (PDT) [thread overview]
Message-ID: <20061020.152247.111203913.davem@davemloft.net> (raw)
In-Reply-To: <Pine.LNX.4.64.0610201500040.3962@g5.osdl.org>
From: Linus Torvalds <torvalds@osdl.org>
Date: Fri, 20 Oct 2006 15:02:39 -0700 (PDT)
> On Fri, 20 Oct 2006, Ralf Baechle wrote:
> > When I delete the call (not part of my patchset) it means 12% faster
> > fork. But I'm not proposing this for 2.6.19.
>
> I just suspect it means a _buggy_ fork.
>
> It so happens (I think), that fork is big enough that it probably flushes
> the L1 cache _anyway_.
My understanding is that this works because in Ralf's original patch
(which is the context in which he is removing the flush_cache_mm()
call), he uses kmap()/kunmap() to map the page(s) being accessed at a
kernel virtual address which will fall into the same cache color as
the user virtual address --> no alias problems.
Since he does this for every page touched on the kernel side during
dup_mmap(), the existing flush_cache_mm() call in dup_mmap() does in
fact become redundant.
next prev parent reply other threads:[~2006-10-20 22:22 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-19 16:35 Ralf Baechle
2006-10-19 16:35 ` [PATCH 2/3] Pass vma argument to copy_user_highpage() Ralf Baechle
2006-10-19 16:35 ` [PATCH 3/3] MIPS: Fix COW D-cache aliasing on fork Ralf Baechle
2006-10-22 2:32 ` Ralf Baechle
2006-10-19 17:46 ` [PATCH 1/3] " Nick Piggin
2006-10-19 18:13 ` Ralf Baechle
2006-10-19 18:48 ` Nick Piggin
2006-10-19 22:59 ` David Miller
2006-10-20 14:39 ` Nick Piggin
2006-10-20 15:49 ` Linus Torvalds
2006-10-20 15:57 ` Nick Piggin
2006-10-20 16:36 ` Linus Torvalds
2006-10-20 16:47 ` Nick Piggin
2006-10-20 17:16 ` Linus Torvalds
2006-10-20 17:37 ` Nick Piggin
2006-10-21 0:46 ` Ralf Baechle
2006-10-20 19:36 ` David Miller
2006-10-20 19:54 ` Linus Torvalds
2006-10-20 19:58 ` David Miller
2006-10-20 20:10 ` Linus Torvalds
2006-10-20 20:59 ` Russell King
2006-10-20 21:06 ` David Miller
2006-10-20 21:17 ` Russell King
2006-10-20 21:30 ` David Miller
2006-10-20 21:12 ` Linus Torvalds
2006-10-20 21:28 ` Russell King
2006-10-20 21:41 ` Ralf Baechle
2006-10-21 16:28 ` Atsushi Nemoto
2006-10-20 21:49 ` Ralf Baechle
2006-10-20 22:02 ` Linus Torvalds
2006-10-20 22:22 ` David Miller [this message]
2006-10-20 22:51 ` Ralf Baechle
2006-10-20 23:28 ` Linus Torvalds
2006-10-21 0:06 ` Ralf Baechle
2006-10-21 0:38 ` Linus Torvalds
2006-10-21 1:29 ` Paul Mackerras
2006-10-21 2:11 ` David Miller
2006-10-21 2:37 ` Linus Torvalds
2006-10-21 2:46 ` David Miller
2006-10-21 18:27 ` Ralf Baechle
2006-10-22 1:34 ` Ralf Baechle
2006-12-02 9:49 ` Russell King
2006-10-23 8:50 ` Martin Schwidefsky
2006-10-20 16:05 ` Ralf Baechle
2006-10-20 16:30 ` Nick Piggin
2006-10-20 19:23 ` David Miller
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