Re: [PATCH] arch/x86: use kernel_fpu_[begin|end] for RAID5 checksumming

[H. Peter Anvin]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 05/02/2012 09:57 PM, NeilBrown wrote:
> On Mon, 30 Apr 2012 16:51:15 -0700 Jim Kukunas 
> <james.t.kukunas@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> 
> 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
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
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=wGxV
-----END PGP SIGNATURE-----
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/