Re: [PATCH -v2] vmx: increase ple_gap default to 64

Avi Kivity
2011-01-16T15:42:57Z

On 01/04/2011 04:51 PM, Rik van Riel wrote:
> On some CPUs, a ple_gap of 41 is simply insufficient to ever trigger
> PLE exits, even with the minimalistic PLE test from kvm-unit-tests.
>
> http://git.kernel.org/?p=virt/kvm/kvm-unit-tests.git;a=commitdiff;h=eda71b28fa122203e316483b35f37aaacd42f545
>
> For example, the Xeon X5670 CPU needs a ple_gap of at least 48 in
> order to get pause loop exits:
>
> # modprobe kvm_intel ple_gap=47
> # taskset 1 /usr/local/bin/qemu-system-x86_64 -device testdev,chardev=log -chardev stdio,id=log -kernel x86/vmexit.flat -append ple-round-robin -smp 2
> VNC server running on `::1:5900'
> enabling apic
> enabling apic
> ple-round-robin 58298446
> # rmmod kvm_intel
> # modprobe kvm_intel ple_gap=48
> # taskset 1 /usr/local/bin/qemu-system-x86_64 -device testdev,chardev=log -chardev stdio,id=log -kernel x86/vmexit.flat -append ple-round-robin -smp 2
> VNC server running on `::1:5900'
> enabling apic
> enabling apic
> ple-round-robin 36616
>
> Increase the ple_gap to 128 to be on the safe side. Is this enough
> for a CPU with HT that has a busy sibling thread, or should it be
> even larger? On the X5670, loading up the sibling thread with an
> infinite loop does not seem to increase the required ple_gap.
>

Applied, thanks.

--
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