Re: [PATCH RFC 0/5] apic: eoi optimization support

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, May 07, 2012 at 12:35:12PM +0200, Ingo Molnar wrote:
> > Michael S. Tsirkin (5):
> >   apic: fix typo EIO_ACK -> EOI_ACK and document
> >   apic: use symbolic APIC_EOI_ACK
> >   x86: add apic->eoi_write callback
> >   x86: eoi micro-optimization
> >   kvm_para: guest side for eoi avoidance
> > 
> >  arch/x86/include/asm/apic.h            |   22 ++++++++++++--
> >  arch/x86/include/asm/apicdef.h         |    2 +-
> >  arch/x86/include/asm/bitops.h          |    6 ++-
> >  arch/x86/include/asm/kvm_para.h        |    2 +
> >  arch/x86/kernel/apic/apic_flat_64.c    |    2 +
> >  arch/x86/kernel/apic/apic_noop.c       |    1 +
> >  arch/x86/kernel/apic/apic_numachip.c   |    1 +
> >  arch/x86/kernel/apic/bigsmp_32.c       |    1 +
> >  arch/x86/kernel/apic/es7000_32.c       |    2 +
> >  arch/x86/kernel/apic/numaq_32.c        |    1 +
> >  arch/x86/kernel/apic/probe_32.c        |    1 +
> >  arch/x86/kernel/apic/summit_32.c       |    1 +
> >  arch/x86/kernel/apic/x2apic_cluster.c  |    1 +
> >  arch/x86/kernel/apic/x2apic_phys.c     |    1 +
> >  arch/x86/kernel/apic/x2apic_uv_x.c     |    1 +
> >  arch/x86/kernel/kvm.c                  |   51 ++++++++++++++++++++++++++++++--
> >  arch/x86/platform/visws/visws_quirks.c |    2 +-
> >  17 files changed, 88 insertions(+), 10 deletions(-)
> 
> No objections from the x86 side.

Is kvm.git a good tree to merge this through?

> In terms of advantages, could you please create perf stat runs 
> that counts the number of MMIOs or so? That should show a pretty 
> obvious improvement - and that is enough as proof, no need to 
> try to reproduce the performance win in a noisy benchmark.

You mean with kvm PV, right? On real hardware the micro-optimization
removes branches and maybe cache-misses but I don't see why would it
reduce MMIOs.

-- 
MST