From: "H. Peter Anvin" <hpa@zytor.com>
To: NeilBrown <neilb@suse.de>
Cc: Jim Kukunas <james.t.kukunas@linux.intel.com>,
linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arch/x86: use kernel_fpu_[begin|end] for RAID5 checksumming
Date: Wed, 02 May 2012 23:43:33 -0700 [thread overview]
Message-ID: <4FA22915.6050400@zytor.com> (raw)
In-Reply-To: <20120503145744.4e425dd5@notabene.brown>
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On 05/02/2012 09:57 PM, NeilBrown wrote:
> On Mon, 30 Apr 2012 16:51:15 -0700 Jim Kukunas
> <james.t.kukunas@linux.intel.com> wrote:
>
>> Currently, the SSE and AVX xor functions manually save and
>> restore the [X|Y]MM registers. Instead, we should use
>> kernel_fpu_[begin|end].
>>
>> This patch sacrifices some throughput,~5-10% for AVX and ~2% for
>> SSE, in exchange for safety against future FPU corruption bugs.
>>
>> Patch applies to md/for-next.
>>
>> Signed-off-by: Jim Kukunas <james.t.kukunas@linux.intel.com>
>
> Hi Jim, I'm really not able to assess the validity of this patch.
> I don't doubt it exactly, but I'd value a second opinion just to
> be confident. Peter: can you review and comment?
>
> Thanks, NeilBrown
>
Are these functions ever called with unaligned arguments?
Other than that, the patch is correct, and is the preferred way to do
this, but I'm unhappy about the cost. I have suggested to Jim a few
ways by which we might be able to mitigate the cost or even improve
performance, but the implementation depends very much on the above
question (unlike the RAID-6 code, which assumes aligned buffers at all
times.)
-hpa
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prev parent reply other threads:[~2012-05-03 6:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-30 23:51 [PATCH] arch/x86: use kernel_fpu_[begin|end] for RAID5 checksumming Jim Kukunas
2012-05-03 4:57 ` NeilBrown
2012-05-03 6:43 ` H. Peter Anvin [this message]
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