| Message ID | 20120710193138.16440.31791.sendpatchset@codeblue (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/10/2012 03:31 PM, Raghavendra K T wrote: > From: Raghavendra K T<raghavendra.kt@linux.vnet.ibm.com> > > Currently PLE handler can repeatedly do a directed yield to same vcpu > that has recently done PL exit. This can degrade the performance. > > Try to yield to most eligible guy instead by alternate yielding. > Precisely, give chance to a VCPU which has: > (a) Not done PLE exit at all (probably he is preempted lock-holder) > (b) VCPU skipped in last iteration because it did PL exit, and probably > has become eligible now (next eligible lock holder) > > Signed-off-by: Raghavendra K T<raghavendra.kt@linux.vnet.ibm.com> Reviewed-by: Rik van Riel <riel@redhat.com>
* Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> wrote: > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1595,6 +1595,9 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me) > continue; > if (waitqueue_active(&vcpu->wq)) > continue; > + if (!kvm_arch_vcpu_check_and_update_eligible(vcpu)) { > + continue; > + } Saw this fly by for a second time and now it annoyed me enough to mention it: those curly braces are superfluous and should be dropped. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 07/11/2012 02:20 AM, Ingo Molnar wrote: > > * Raghavendra K T<raghavendra.kt@linux.vnet.ibm.com> wrote: > >> --- a/virt/kvm/kvm_main.c >> +++ b/virt/kvm/kvm_main.c >> @@ -1595,6 +1595,9 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me) >> continue; >> if (waitqueue_active(&vcpu->wq)) >> continue; >> + if (!kvm_arch_vcpu_check_and_update_eligible(vcpu)) { >> + continue; >> + } > > Saw this fly by for a second time and now it annoyed me enough > to mention it: those curly braces are superfluous and should be > dropped. > Oops! Sorry.will remove {} and resend with Rik's reviewed-by. TBH, block got simplified after iterations (local), this one leftout. my mistake. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index dd17537..884f2c4 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -256,5 +256,10 @@ struct kvm_arch{ struct gmap *gmap; }; +static inline bool kvm_arch_vcpu_check_and_update_eligible(struct kvm_vcpu *v) +{ + return true; +} + extern int sie64a(struct kvm_s390_sie_block *, u64 *); #endif diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 386f3e6..77c1358 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -966,7 +966,7 @@ extern bool kvm_find_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn); void kvm_complete_insn_gp(struct kvm_vcpu *vcpu, int err); int kvm_is_in_guest(void); - +bool kvm_arch_vcpu_check_and_update_eligible(struct kvm_vcpu *vcpu); void kvm_pmu_init(struct kvm_vcpu *vcpu); void kvm_pmu_destroy(struct kvm_vcpu *vcpu); void kvm_pmu_reset(struct kvm_vcpu *vcpu); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b30c310..bf92ffc 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6623,6 +6623,36 @@ bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu) kvm_x86_ops->interrupt_allowed(vcpu); } +/* + * Helper that checks whether a VCPU is eligible for directed yield. + * Most eligible candidate to yield is decided by following heuristics: + * + * (a) VCPU which has not done PL exit recently (preempted lock holder), + * indicated by @pause_loop_exited. Cleared just before guest_enter() + * + * (b) VCPU which has done PL exit but did not get chance last time. + * (mostly it has become eligible now since we have probably + * yielded to lockholder in last iteration. This is done by toggling + * @dy_eligible each time a VCPU checked for eligibility.) + * + * Yielding to a recently PL exited VCPU before yielding to preempted + * lock-holder results in uneligible VCPU burning CPU. Giving priority + * for a potential lock-holder increases lock progress chance. + */ +bool kvm_arch_vcpu_check_and_update_eligible(struct kvm_vcpu *vcpu) +{ + bool eligible; + + eligible = !vcpu->arch.ple.pause_loop_exited || + (vcpu->arch.ple.pause_loop_exited && + vcpu->arch.ple.dy_eligible); + + if (vcpu->arch.ple.pause_loop_exited) + vcpu->arch.ple.dy_eligible = !vcpu->arch.ple.dy_eligible; + + return eligible; +} + EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit); EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq); EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_page_fault); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 7e14068..519321a 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1595,6 +1595,9 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me) continue; if (waitqueue_active(&vcpu->wq)) continue; + if (!kvm_arch_vcpu_check_and_update_eligible(vcpu)) { + continue; + } if (kvm_vcpu_yield_to(vcpu)) { kvm->last_boosted_vcpu = i; yielded = 1;