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SubjectRe: [RFC PATCH 0/4] Gang scheduling in CFS
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On Mon, 02 Jan 2012 11:37:22 +0200, Avi Kivity <avi@redhat.com> wrote:
> On 12/31/2011 04:21 AM, Nikunj A Dadhania wrote:
> >
> > GangV2:
> > 27.45% ebizzy libc-2.12.so [.] __memcpy_ssse3_back
> > 12.12% ebizzy [kernel.kallsyms] [k] clear_page
> > 9.22% ebizzy [kernel.kallsyms] [k] __do_page_fault
> > 6.91% ebizzy [kernel.kallsyms] [k] flush_tlb_others_ipi
> > 4.06% ebizzy [kernel.kallsyms] [k] get_page_from_freelist
> > 4.04% ebizzy [kernel.kallsyms] [k] ____pagevec_lru_add
> >
> > GangBase:
> > 45.08% ebizzy [kernel.kallsyms] [k] flush_tlb_others_ipi
> > 15.38% ebizzy libc-2.12.so [.] __memcpy_ssse3_back
> > 7.00% ebizzy [kernel.kallsyms] [k] clear_page
> > 4.88% ebizzy [kernel.kallsyms] [k] __do_page_fault
>
> Looping in flush_tlb_others(). Rik, what trace an we run to find out
> why PLE directed yield isn't working as expected?
>
I tried some experiments by adding a pause_loop_exits stat in the
kvm_vpu_stat.

Here are some observation related to Baseline-only(8vm case)

| ple_gap=128 | ple_gap=64 | ple_gap=256 | ple_window=2048
--------------+-------------+------------+-------------+----------------
EbzyRecords/s | 2247.50 | 2132.75 | 2086.25 | 1835.62
PauseExits | 7928154.00 | 6696342.00 | 7365999.00 | 50319582.00

With ple_window = 2048, PauseExits is more than 6times the default case

-----

From: Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com>

Add Pause-loop-exit stats to kvm_vcpu_stat

Signed-off-by: Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com>


diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b4973f4..be2e7f2 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -539,6 +539,7 @@ struct kvm_vcpu_stat {
u32 hypercalls;
u32 irq_injections;
u32 nmi_injections;
+ u32 pause_loop_exits;
};

struct x86_instruction_info;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 579a0b5..29e90b7 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4897,6 +4897,8 @@ out:
static int handle_pause(struct kvm_vcpu *vcpu)
{
skip_emulated_instruction(vcpu);
+ ++vcpu->stat.pause_loop_exits;
kvm_vcpu_on_spin(vcpu);

return 1;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c38efd7..87433a8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -149,6 +149,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "mmu_unsync", VM_STAT(mmu_unsync) },
{ "remote_tlb_flush", VM_STAT(remote_tlb_flush) },
{ "largepages", VM_STAT(lpages) },
+ { "pause_loop_exits", VCPU_STAT(pause_loop_exits) },
{ NULL }
};


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