Window is increased on every PLE exit and decreased on every sched_in. The idea is that we don't want to PLE exit if there is no preemption going on. We do this with sched_in() because it does not hold rq lock.
There are two new kernel parameters for changing the window: ple_window_grow and ple_window_shrink ple_window_grow affects the window on PLE exit and ple_window_shrink does it on sched_in; depending on their value, the window is modifier like this: (ple_window is kvm_intel's global) ple_window_shrink/ | ple_window_grow | PLE exit | sched_in -------------------+--------------------+--------------------- < 1 | = ple_window | = ple_window < ple_window | *= ple_window_grow | /= ple_window_shrink otherwise | += ple_window_grow | -= ple_window_shrink A third new parameter, ple_window_max, controls a maximal ple_window. A minimum equals to ple_window. Signed-off-by: Radim Krčmář <rkrc...@redhat.com> --- arch/x86/kvm/vmx.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 78 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 18e0e52..e63d7ac 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -125,14 +125,32 @@ module_param(nested, bool, S_IRUGO); * 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 128 -#define KVM_VMX_DEFAULT_PLE_WINDOW 4096 +#define KVM_VMX_DEFAULT_PLE_GAP 128 +#define KVM_VMX_DEFAULT_PLE_WINDOW 4096 +#define KVM_VMX_DEFAULT_PLE_WINDOW_GROW 2 +#define KVM_VMX_DEFAULT_PLE_WINDOW_SHRINK 0 +#define KVM_VMX_DEFAULT_PLE_WINDOW_MAX \ + INT_MAX / KVM_VMX_DEFAULT_PLE_WINDOW_GROW + static int ple_gap = KVM_VMX_DEFAULT_PLE_GAP; module_param(ple_gap, int, S_IRUGO); static int ple_window = KVM_VMX_DEFAULT_PLE_WINDOW; module_param(ple_window, int, S_IRUGO); +/* Default doubles per-vcpu window every exit. */ +static int ple_window_grow = KVM_VMX_DEFAULT_PLE_WINDOW_GROW; +module_param(ple_window_grow, int, S_IRUGO); + +/* Default resets per-vcpu window every exit to ple_window. */ +static int ple_window_shrink = KVM_VMX_DEFAULT_PLE_WINDOW_SHRINK; +module_param(ple_window_shrink, int, S_IRUGO); + +/* Default is to compute the maximum so we can never overflow. */ +static int ple_window_actual_max = KVM_VMX_DEFAULT_PLE_WINDOW_MAX; +static int ple_window_max = KVM_VMX_DEFAULT_PLE_WINDOW_MAX; +module_param(ple_window_max, int, S_IRUGO); + extern const ulong vmx_return; #define NR_AUTOLOAD_MSRS 8 @@ -5679,12 +5697,66 @@ out: return ret; } +static int __grow_ple_window(int val) +{ + if (ple_window_grow < 1) + return ple_window; + + val = min(val, ple_window_actual_max); + + if (ple_window_grow < ple_window) + val *= ple_window_grow; + else + val += ple_window_grow; + + return val; +} + +static int __shrink_ple_window(int val, int shrinker, int minimum) +{ + if (shrinker < 1) + return ple_window; + + if (shrinker < ple_window) + val /= shrinker; + else + val -= shrinker; + + return max(val, minimum); +} + +static void modify_ple_window(struct kvm_vcpu *vcpu, int grow) +{ + struct vcpu_vmx *vmx = to_vmx(vcpu); + int new; + + if (grow) + new = __grow_ple_window(vmx->ple_window); + else + new = __shrink_ple_window(vmx->ple_window, ple_window_shrink, + ple_window); + + vmx->ple_window = max(new, ple_window); +} +#define grow_ple_window(vcpu) modify_ple_window(vcpu, 1) +#define shrink_ple_window(vcpu) modify_ple_window(vcpu, 0) + +static void update_ple_window_actual_max(void) +{ + ple_window_actual_max = + __shrink_ple_window(max(ple_window_max, ple_window), + ple_window_grow, INT_MIN); +} + /* * Indicate a busy-waiting vcpu in spinlock. We do not enable the PAUSE * exiting, so only get here on cpu with PAUSE-Loop-Exiting. */ static int handle_pause(struct kvm_vcpu *vcpu) { + if (ple_gap) + grow_ple_window(vcpu); + skip_emulated_instruction(vcpu); kvm_vcpu_on_spin(vcpu); @@ -8854,6 +8926,8 @@ static int vmx_check_intercept(struct kvm_vcpu *vcpu, void vmx_sched_in(struct kvm_vcpu *vcpu, int cpu) { + if (ple_gap) + shrink_ple_window(vcpu); } static struct kvm_x86_ops vmx_x86_ops = { @@ -9077,6 +9151,8 @@ static int __init vmx_init(void) } else kvm_disable_tdp(); + update_ple_window_actual_max(); + return 0; out7: -- 2.0.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html