Re: CFR: unifing sha256 userland/kernel implementation...

John-Mark Gurney wrote this message on Tue, Feb 11, 2014 at 10:56 -0800:
> I did some performance testing on sha256, and found that the libmd
> version is significantly faster, ~20%, than the kernel version.  Even
> if you enable SHA2_UNROLL_TRANSFORM (which isn't the default), the
> version in libmd is still faster.
> 
> So, this patch moves libmd's sha256c.c and sha256.h into the kernel,
> and adapts the userland to pull the version from the kernel.  This
> change removes sha256 from the existing sha2.c file, and does some
> minor cleanup of types in sha2.
> 
> I have tested this w/ ZFS using sha256 checksums, and a ZFS made
> pre-patch is read fine by a kernel post patch.  I have also run
> the tests in lib/libmd and they all pass fine.  Passes
> buildworld/buildkernel/installkernel/reboot/installworld/reboot/test.
> 
> Patch:
> https://www.funkthat.com/~jmg/sha256.kern.patch
> 
> Following stats are in seconds to digest 100000 10000-byte blocks,
> calculated using sha256 -t:
> $ ministat soft.times kernsoft.times 
> x soft.times
> + kernsoft.times
> +------------------------------------------------------------------------------+
> |x                   xx      xx             +++  +                            +|
> |        |___________AM_________|     |_______M_____A______________|           |
> +------------------------------------------------------------------------------+
>     N           Min           Max        Median           Avg        Stddev
> x   5      6.775387      8.279581      7.848128      7.792094    0.60912664
> +   5      8.997429     10.768921      9.090787     9.4359144    0.75040822
> Difference at 95.0% confidence
>         1.64382 +/- 0.99674
>         21.096% +/- 12.7917%
>         (Student's t, pooled s = 0.683428)
> 
> This is in preperation of bringing in an SSE4 accelerated version of
> sha256 (for both userland and kernel) that sees a 2x performance
> increase.

Sorry, security@ != freebsd-security@...  This is now going to the
correct email..

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."
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