linux-kernel - Re: [X86] PCI: Use generic cacheline sizing instead of per-vendor tests.

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Message-ID: <20091014213742.GA17311@redhat.com>
Date:	Wed, 14 Oct 2009 17:37:42 -0400
From:	Dave Jones <davej@...hat.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [X86] PCI: Use generic cacheline sizing instead of per-vendor
	tests.

On Wed, Oct 14, 2009 at 02:30:54PM -0700, Jesse Barnes wrote:
 > On Wed, 14 Oct 2009 16:31:39 -0400
 > Dave Jones <davej@...hat.com> wrote:
 > 
 > > Instead of the PCI code needing to have code to determine the 
 > > cacheline size of each processor, use the data the cpu identification
 > > code should have already determined during early boot.
 > > 
 > > (The vendor checks are also incomplete, and don't take into account
 > >  modern CPUs)
 > > 
 > > I've been carrying a variant of this code in Fedora for a while,
 > > that prints debug information.  There are a number of cases where we
 > > are currently setting the PCI cacheline size to 32 bytes, when the CPU
 > > cacheline size is 64 bytes.  With this patch, we set them both the
 > > same.
 > > 
 > > Signed-off-by: Dave Jones <davej@...hat.com>
 > > 
 > 
 > Does this improve performance enough to warrant putting it into the
 > current cycle?  Or is queuing it for 2.6.33 sufficient?

I haven't done any performance testing with/without. My intentions
were purely from a correctness standpoint. 

It's not critical, and we've lived with this bug for a long time,
so waiting is fine.

	Dave

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