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| author | Rik van Riel <riel@redhat.com> | 2011-01-04 14:51:33 (GMT) |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2011-03-17 16:08:25 (GMT) |
| commit | 00c25bce02fde63eaa1227532cff9ac7b71de79e (patch) | |
| tree | bf04cb749e0ff1913cffe8aa13af9794116b5e44 | |
| parent | 3781c01c1574a2cd58fd5ba2bf58c710edff3da5 (diff) | |
| download | linux-00c25bce02fde63eaa1227532cff9ac7b71de79e.tar.xz | |
KVM: VMX: increase ple_gap default to 128
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.
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Zhai, Edwin <edwin.zhai@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
| -rw-r--r-- | arch/x86/kvm/vmx.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 87ad551..e2c4e32 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -93,14 +93,14 @@ module_param(yield_on_hlt, bool, S_IRUGO); * These 2 parameters are used to config the controls for Pause-Loop Exiting: * ple_gap: upper bound on the amount of time between two successive * executions of PAUSE in a loop. Also indicate if ple enabled. - * According to test, this time is usually small than 41 cycles. + * According to test, this time is usually smaller than 128 cycles. * ple_window: upper bound on the amount of time a guest is allowed to execute * in a PAUSE loop. Tests indicate that most spinlocks are held for * less than 2^12 cycles * Time is measured based on a counter that runs at the same rate as the TSC, * refer SDM volume 3b section 21.6.13 & 22.1.3. */ -#define KVM_VMX_DEFAULT_PLE_GAP 41 +#define KVM_VMX_DEFAULT_PLE_GAP 128 #define KVM_VMX_DEFAULT_PLE_WINDOW 4096 static int ple_gap = KVM_VMX_DEFAULT_PLE_GAP; module_param(ple_gap, int, S_IRUGO); |