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From: Stephen Hemminger <shemminger@vyatta.com>
To: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: davem@davemloft.net, netdev@vger.kernel.org, gospo@redhat.com,
	bphilips@novell.com, Andi Kleen <ak@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Alexander Duyck <alexander.h.duyck@intel.com>
Subject: Re: [net-next-2.6 PATCH] x86: Drop CONFIG_MCORE2 check around setting of NET_IP_ALIGN
Date: Thu, 1 Jul 2010 17:26:54 -0700	[thread overview]
Message-ID: <20100701172654.713b6043@nehalam> (raw)
In-Reply-To: <20100701232742.15934.49030.stgit@localhost.localdomain>

On Thu, 01 Jul 2010 16:28:27 -0700
Jeff Kirsher <jeffrey.t.kirsher@intel.com> wrote:

> From: Alexander Duyck <alexander.h.duyck@intel.com>
> 
> This patch removes the CONFIG_MCORE2 check from around NET_IP_ALIGN.  It is
> based on a suggestion from Andi Kleen.  The assumption is that there are
> not any x86 cores where unaligned access is really slow, and this change
> would allow for a performance improvement to still exist on configurations
> that are not necessarily optimized for Core 2.
> 
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: x86@kernel.org
> Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> ---

This is a good idea, but warnig it may end up masking broken
hardware. Developers of new drivers will end up never
exercising unaligned DMA, resulting in hardware 
that doesn't work on platforms that have NET_IP_ALIGN set
to 2.

-- 

  reply	other threads:[~2010-07-02  0:26 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-07-01 23:28 [net-next-2.6 PATCH] x86: Drop CONFIG_MCORE2 check around setting of NET_IP_ALIGN Jeff Kirsher
2010-07-02  0:26 ` Stephen Hemminger [this message]
2010-07-02  1:15 ` H. Peter Anvin
2010-07-02  5:49 ` David Miller

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