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| Started by | Andres Oportus <andresoportus@android.com> |
|---|---|
| First post | 2017-08-01 06:20 +0200 |
| Last post | 2017-08-04 22:00 +0200 |
| Articles | 3 — 3 participants |
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[stable 4.4: PATCH] sched/cputime: Fix prev steal time accouting during CPU hotplug Andres Oportus <andresoportus@android.com> - 2017-08-01 06:20 +0200
Re: [stable 4.4: PATCH] sched/cputime: Fix prev steal time accouting during CPU hotplug Paolo Bonzini <pbonzini@redhat.com> - 2017-08-02 18:50 +0200
Re: [stable 4.4: PATCH] sched/cputime: Fix prev steal time accouting during CPU hotplug Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-04 22:00 +0200
| From | Andres Oportus <andresoportus@android.com> |
|---|---|
| Date | 2017-08-01 06:20 +0200 |
| Subject | [stable 4.4: PATCH] sched/cputime: Fix prev steal time accouting during CPU hotplug |
| Message-ID | <u9wP0-6U8-5@gated-at.bofh.it> |
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 <wanpeng.li@hotmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 'commit e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU hotplug")'
Link: http://lkml.kernel.org/r/1465813966-3116-3-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andres Oportus <andresoportus@google.com>
---
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
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| From | Paolo Bonzini <pbonzini@redhat.com> |
|---|---|
| Date | 2017-08-02 18:50 +0200 |
| Subject | Re: [stable 4.4: PATCH] sched/cputime: Fix prev steal time accouting during CPU hotplug |
| Message-ID | <ua50m-3TJ-9@gated-at.bofh.it> |
| In reply to | #1700609 |
On 02/08/2017 18:36, Andres Oportus wrote:
> +Paolo Bonzini
>
> On Mon, Jul 31, 2017 at 9:18 PM, Andres Oportus
> <andresoportus@android.com <mailto:andresoportus@android.com>> 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 <pbonzini@redhat.com>
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 <wanpeng.li@hotmail.com
> <mailto:wanpeng.li@hotmail.com>>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org
> <mailto:peterz@infradead.org>>
> Acked-by: Paolo Bonzini <pbonzini@redhat.com
> <mailto:pbonzini@redhat.com>>
> Cc: Frederic Weisbecker <fweisbec@gmail.com <mailto:fweisbec@gmail.com>>
> Cc: Linus Torvalds <torvalds@linux-foundation.org
> <mailto:torvalds@linux-foundation.org>>
> Cc: Mike Galbraith <efault@gmx.de <mailto:efault@gmx.de>>
> Cc: Peter Zijlstra <peterz@infradead.org <mailto:peterz@infradead.org>>
> Cc: Radim Krčmář <rkrcmar@redhat.com <mailto:rkrcmar@redhat.com>>
> Cc: Rik van Riel <riel@redhat.com <mailto:riel@redhat.com>>
> Cc: Thomas Gleixner <tglx@linutronix.de <mailto:tglx@linutronix.de>>
> Fixes: 'commit e9532e69b8d1 ("sched/cputime: Fix steal time
> accounting vs. CPU hotplug")'
> Link:
> http://lkml.kernel.org/r/1465813966-3116-3-git-send-email-wanpeng.li@hotmail.com
> <http://lkml.kernel.org/r/1465813966-3116-3-git-send-email-wanpeng.li@hotmail.com>
> Signed-off-by: Ingo Molnar <mingo@kernel.org <mailto:mingo@kernel.org>>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org
> <mailto:gregkh@linuxfoundation.org>>
> Signed-off-by: Andres Oportus <andresoportus@google.com
> <mailto:andresoportus@google.com>>
> ---
> 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
>
>
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| From | Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
|---|---|
| Date | 2017-08-04 22:00 +0200 |
| Subject | Re: [stable 4.4: PATCH] sched/cputime: Fix prev steal time accouting during CPU hotplug |
| Message-ID | <uaQVj-2UY-7@gated-at.bofh.it> |
| In reply to | #1702267 |
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 > > <andresoportus@android.com <mailto:andresoportus@android.com>> 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 <pbonzini@redhat.com> Thanks for the review, now queued up. greg k-h
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