Re: [Qemu-devel] [PATCH v5 0/2] add avx2 instruction optimization

[Amit Shah]

On (Mon) 22 Feb 2016 [06:23:54], Li, Liang Z wrote:
> > On 27/01/2016 08:33, Liang Li wrote:
> > > buffer_find_nonzero_offset() is a hot function during live migration.
> > > Now it use SSE2 instructions for optimization. For platform supports
> > > AVX2 instructions, use the AVX2 instructions for optimization can help
> > > to improve the performance of zero page checking about 30% comparing
> > > to SSE2.
> > > Live migration can be faster with this optimization, the test result
> > > shows that for an 8GB RAM idle guest, this patch can help to shorten
> > > the total live migration time about 6%.
> > >
> > > This patch use the ifunc mechanism to select the proper function when
> > > running, for platform supports AVX2, execute the AVX2 instructions,
> > > else, execute the original instructions.
> > >
> > > With this patch, the QEMU binary can run on both platforms support
> > > AVX2 or not.
> > >
> > > Compiler which doesn't support the AVX2 and ifunc attribute can also
> > > build the source code successfully.
> > >
> > > v5 -> v4 changes:
> > >   * Enhance the ifunc attribute detection (Paolo's suggestion)
> > >
> > > v3 -> v4 changes:
> > >   * Use the GCC #pragma to make things simple (Paolo's suggestion)
> > >   * Put avx2 related code in cutils.c (Richard's suggestion)
> > >   * Change the configure, detect ifunc and avx2 attributes together
> > >
> > > v2 -> v3 changes:
> > >   * Detect the ifunc attribute support (Paolo's suggestion)
> > >   * Use the ifunc attribute instead of the inline asm (Richard's 
> > > suggestion)
> > >   * Change the configure (Juan's suggestion)
> > >
> > > Liang Li (2):
> > >   configure: detect ifunc and avx2 attribute
> > >   cutils: add avx2 instruction optimization
> > >
> > >  configure             |  21 +++++++++
> > >  include/qemu-common.h |   8 +---
> > >  util/cutils.c         | 118
> > ++++++++++++++++++++++++++++++++++++++++++++++++--
> > >  3 files changed, 136 insertions(+), 11 deletions(-)
> > 
> > Reviewed-by: Paolo Bonzini <address@hidden>
> 
> This patch set is pending here for a long time,  who can help to make it 
> merged?

Not sure; I could take it from the migration tree if no one objects.


                Amit