linux-kernel - Re: [PATCH 1/3] Fix COW D-cache aliasing on fork

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Message-ID: <20061021182701.GA22194@linux-mips.org>
Date:	Sat, 21 Oct 2006 19:27:01 +0100
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	Linus Torvalds <torvalds@...l.org>
Cc:	David Miller <davem@...emloft.net>, nickpiggin@...oo.com.au,
	akpm@...l.org, linux-kernel@...r.kernel.org, anemo@....ocn.ne.jp,
	linux-arch@...r.kernel.org, schwidefsky@...ibm.com,
	James.Bottomley@...elEye.com
Subject: Re: [PATCH 1/3] Fix COW D-cache aliasing on fork

On Fri, Oct 20, 2006 at 07:37:24PM -0700, Linus Torvalds wrote:

> Well, if you can re-create the performance numbers (Ralf - can you send 
> the full series with the final "remove the now unnecessary flush" to 
> Davem?), that will make deciding things easier, I think.
> 
> I suspect sparc, mips and arm are the main architectures where virtually 
> indexed caching really matters enough for this to be an issue at all.

What I was using for my fork benchmark was basically the series as posted
in this thread + the quick hack patch below.

I'll dig up some numbers for the posted patchset and will send them later.

   Ralf

diff --git a/kernel/fork.c b/kernel/fork.c
index 29ebb30..c83d226 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -202,7 +202,6 @@ static inline int dup_mmap(struct mm_str
 	struct mempolicy *pol;
 
 	down_write(&oldmm->mmap_sem);
-	flush_cache_mm(oldmm);
 	/*
 	 * Not linked in yet - no deadlock potential:
 	 */
-
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