| Message ID | 1465813966-3116-2-git-send-email-wanpeng.li@hotmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 13/06/2016 12:32, Wanpeng Li wrote: > From: Wanpeng Li <wanpeng.li@hotmail.com> > > Sometimes, after CPU hotplug you can observe a spike in stolen time > (100%) followed by the CPU being marked as 100% idle when it's actually > busy with a CPU hog task. The trace looks like the following: > > cpuhp/1-12 [001] d.h1 167.461657: account_process_tick: steal = 1291385514, prev_steal_time = 0 > cpuhp/1-12 [001] d.h1 167.461659: account_process_tick: steal_jiffies = 1291 > <idle>-0 [001] d.h1 167.462663: account_process_tick: steal = 18732255, prev_steal_time = 1291000000 > <idle>-0 [001] d.h1 167.462664: account_process_tick: steal_jiffies = 18446744072437 > > The sudden decrease of "steal" causes steal_jiffies to underflow. > The root cause is kvm_steal_time being reset to 0 after hot-plugging > back in a CPU. Instead, the preexisting value can be used, which is > what the core scheduler code expects. > > John Stultz also reported a similar issue after guest S3. > > Suggested-by: Paolo Bonzini <pbonzini@redhat.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Radim Krčmář <rkrcmar@redhat.com> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Peter Zijlstra (Intel) <peterz@infradead.org> > Cc: Rik van Riel <riel@redhat.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Frederic Weisbecker <fweisbec@gmail.com> > Cc: John Stultz <john.stultz@linaro.org> > Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> > --- > arch/x86/kernel/kvm.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index eea2a6f..1ef5e48 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -301,8 +301,6 @@ static void kvm_register_steal_time(void) > if (!has_steal_clock) > return; > > - memset(st, 0, sizeof(*st)); > - > wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED)); > pr_info("kvm-stealtime: cpu %d, msr %llx\n", > cpu, (unsigned long long) slow_virt_to_phys(st)); > Because there's no cover letter, I guess I have to ack each patch independently. Acked-by: Paolo Bonzini <pbonzini@redhat.com> Also, there's really no relation between patches 1-2 and 3... Paolo -- 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 Mon, Jun 13, 2016 at 12:44:46PM +0200, Paolo Bonzini wrote: > Because there's no cover letter, I guess I have to ack each patch > independently. > > Acked-by: Paolo Bonzini <pbonzini@redhat.com> Thanks, I'll take the lot through the sched tree. -- 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
2016-06-13 18:44 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>: > > > On 13/06/2016 12:32, Wanpeng Li wrote: >> From: Wanpeng Li <wanpeng.li@hotmail.com> >> >> Sometimes, after CPU hotplug you can observe a spike in stolen time >> (100%) followed by the CPU being marked as 100% idle when it's actually >> busy with a CPU hog task. The trace looks like the following: >> >> cpuhp/1-12 [001] d.h1 167.461657: account_process_tick: steal = 1291385514, prev_steal_time = 0 >> cpuhp/1-12 [001] d.h1 167.461659: account_process_tick: steal_jiffies = 1291 >> <idle>-0 [001] d.h1 167.462663: account_process_tick: steal = 18732255, prev_steal_time = 1291000000 >> <idle>-0 [001] d.h1 167.462664: account_process_tick: steal_jiffies = 18446744072437 >> >> The sudden decrease of "steal" causes steal_jiffies to underflow. >> The root cause is kvm_steal_time being reset to 0 after hot-plugging >> back in a CPU. Instead, the preexisting value can be used, which is >> what the core scheduler code expects. >> >> John Stultz also reported a similar issue after guest S3. >> >> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> >> Cc: Paolo Bonzini <pbonzini@redhat.com> >> Cc: Radim Krčmář <rkrcmar@redhat.com> >> Cc: Ingo Molnar <mingo@kernel.org> >> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> >> Cc: Rik van Riel <riel@redhat.com> >> Cc: Thomas Gleixner <tglx@linutronix.de> >> Cc: Frederic Weisbecker <fweisbec@gmail.com> >> Cc: John Stultz <john.stultz@linaro.org> >> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> >> --- >> arch/x86/kernel/kvm.c | 2 -- >> 1 file changed, 2 deletions(-) >> >> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c >> index eea2a6f..1ef5e48 100644 >> --- a/arch/x86/kernel/kvm.c >> +++ b/arch/x86/kernel/kvm.c >> @@ -301,8 +301,6 @@ static void kvm_register_steal_time(void) >> if (!has_steal_clock) >> return; >> >> - memset(st, 0, sizeof(*st)); >> - >> wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED)); >> pr_info("kvm-stealtime: cpu %d, msr %llx\n", >> cpu, (unsigned long long) slow_virt_to_phys(st)); >> > > Because there's no cover letter, I guess I have to ack each patch > independently. > > Acked-by: Paolo Bonzini <pbonzini@redhat.com> Thanks for your and Rik's review, actually there is a cover letter for this version, it seems that it just send to ML and forgot to Cc maintainers/reviewers. Regards, Wanpeng Li -- 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/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index eea2a6f..1ef5e48 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -301,8 +301,6 @@ static void kvm_register_steal_time(void) if (!has_steal_clock) return; - memset(st, 0, sizeof(*st)); - wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED)); pr_info("kvm-stealtime: cpu %d, msr %llx\n", cpu, (unsigned long long) slow_virt_to_phys(st));