Re: [PATCH RFC 0/5] apic: eoi optimization support
From: Michael S. Tsirkin
Date: Mon May 07 2012 - 06:59:07 EST
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
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