commit 3d89e5478bf550a50c99e93adf659369798263b0 upstream.
Commit:
e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU hotplug")
... set rq->prev_* to 0 after a CPU hotplug comes back, in order to
fix the case where (after CPU hotplug) steal time is smaller than
rq->prev_steal_time.
However, this should never happen. Steal time was only smaller because of the
KVM-specific bug fixed by the previous patch. Worse, the previous patch
triggers a bug on CPU hot-unplug/plug operation: because
rq->prev_steal_time is cleared, all of the CPU's past steal time will be
accounted again on hot-plug.
Since the root cause has been fixed, we can just revert
commit e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU hotplug").
Signed-off-by: Wanpeng Li <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Fixes: 'commit e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU hotplug")'
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Andres Oportus <[email protected]>
---
kernel/sched/core.c | 1 -
kernel/sched/sched.h | 13 -------------
2 files changed, 14 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c436426..b103b9c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5553,7 +5553,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
case CPU_UP_PREPARE:
rq->calc_load_update = calc_load_update;
- account_reset_rq(rq);
break;
case CPU_ONLINE:
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4e5db65..55d92a1 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1770,16 +1770,3 @@ static inline u64 irq_time_read(int cpu)
}
#endif /* CONFIG_64BIT */
#endif /* CONFIG_IRQ_TIME_ACCOUNTING */
-
-static inline void account_reset_rq(struct rq *rq)
-{
-#ifdef CONFIG_IRQ_TIME_ACCOUNTING
- rq->prev_irq_time = 0;
-#endif
-#ifdef CONFIG_PARAVIRT
- rq->prev_steal_time = 0;
-#endif
-#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
- rq->prev_steal_time_rq = 0;
-#endif
-}
--
1.9.1
On 02/08/2017 18:36, Andres Oportus wrote:
> +Paolo Bonzini
>
> On Mon, Jul 31, 2017 at 9:18 PM, Andres Oportus
> <[email protected] <mailto:[email protected]>> wrote:
>
> commit 3d89e5478bf550a50c99e93adf659369798263b0 upstream.
Not an easy call because this is a guest patch that depends on a host
patch. But since it is a corner case (CPU hotplug) and it was
backported to 4.7 already,
Acked-by: Paolo Bonzini <[email protected]>
Paolo
> Commit:
>
> e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU
> hotplug")
>
> ... set rq->prev_* to 0 after a CPU hotplug comes back, in order to
> fix the case where (after CPU hotplug) steal time is smaller than
> rq->prev_steal_time.
>
> However, this should never happen. Steal time was only smaller
> because of the
> KVM-specific bug fixed by the previous patch. Worse, the previous patch
> triggers a bug on CPU hot-unplug/plug operation: because
> rq->prev_steal_time is cleared, all of the CPU's past steal time will be
> accounted again on hot-plug.
>
> Since the root cause has been fixed, we can just revert
> commit e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs.
> CPU hotplug").
>
> Signed-off-by: Wanpeng Li <[email protected]
> <mailto:[email protected]>>
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]
> <mailto:[email protected]>>
> Acked-by: Paolo Bonzini <[email protected]
> <mailto:[email protected]>>
> Cc: Frederic Weisbecker <[email protected] <mailto:[email protected]>>
> Cc: Linus Torvalds <[email protected]
> <mailto:[email protected]>>
> Cc: Mike Galbraith <[email protected] <mailto:[email protected]>>
> Cc: Peter Zijlstra <[email protected] <mailto:[email protected]>>
> Cc: Radim Krčmář <[email protected] <mailto:[email protected]>>
> Cc: Rik van Riel <[email protected] <mailto:[email protected]>>
> Cc: Thomas Gleixner <[email protected] <mailto:[email protected]>>
> Fixes: 'commit e9532e69b8d1 ("sched/cputime: Fix steal time
> accounting vs. CPU hotplug")'
> Link:
> http://lkml.kernel.org/r/[email protected]
> <http://lkml.kernel.org/r/[email protected]>
> Signed-off-by: Ingo Molnar <[email protected] <mailto:[email protected]>>
> Signed-off-by: Greg Kroah-Hartman <[email protected]
> <mailto:[email protected]>>
> Signed-off-by: Andres Oportus <[email protected]
> <mailto:[email protected]>>
> ---
> kernel/sched/core.c | 1 -
> kernel/sched/sched.h | 13 -------------
> 2 files changed, 14 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index c436426..b103b9c 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5553,7 +5553,6 @@ migration_call(struct notifier_block *nfb,
> unsigned long action, void *hcpu)
>
> case CPU_UP_PREPARE:
> rq->calc_load_update = calc_load_update;
> - account_reset_rq(rq);
> break;
>
> case CPU_ONLINE:
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 4e5db65..55d92a1 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1770,16 +1770,3 @@ static inline u64 irq_time_read(int cpu)
> }
> #endif /* CONFIG_64BIT */
> #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
> -
> -static inline void account_reset_rq(struct rq *rq)
> -{
> -#ifdef CONFIG_IRQ_TIME_ACCOUNTING
> - rq->prev_irq_time = 0;
> -#endif
> -#ifdef CONFIG_PARAVIRT
> - rq->prev_steal_time = 0;
> -#endif
> -#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
> - rq->prev_steal_time_rq = 0;
> -#endif
> -}
> --
> 1.9.1
>
>
On Wed, Aug 02, 2017 at 06:46:46PM +0200, Paolo Bonzini wrote:
> On 02/08/2017 18:36, Andres Oportus wrote:
> > +Paolo Bonzini
> >
> > On Mon, Jul 31, 2017 at 9:18 PM, Andres Oportus
> > <[email protected] <mailto:[email protected]>> wrote:
> >
> > commit 3d89e5478bf550a50c99e93adf659369798263b0 upstream.
>
> Not an easy call because this is a guest patch that depends on a host
> patch. But since it is a corner case (CPU hotplug) and it was
> backported to 4.7 already,
>
> Acked-by: Paolo Bonzini <[email protected]>
Thanks for the review, now queued up.
greg k-h