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Groups > linux.kernel > #1219880
| From | Davidlohr Bueso <dave@stgolabs.net> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression |
| Date | 2015-09-07 02:10 +0200 |
| Message-ID | <q5Sat-5Rx-7@gated-at.bofh.it> (permalink) |
| References | (2 earlier) <q4TrX-3vn-9@gated-at.bofh.it> <q4UHo-5cD-15@gated-at.bofh.it> <q50MO-5FD-9@gated-at.bofh.it> <q50Wu-5QK-11@gated-at.bofh.it> <q516c-61Z-29@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Fri, 04 Sep 2015, Peter Zijlstra wrote:
>-static inline bool virt_queued_spin_lock(struct qspinlock *lock)
>+static inline bool virt_spin_lock(struct qspinlock *lock)
Given that we fall back to the cmpxchg loop even when PARAVIRT is not in the
picture, I believe this function is horribly misnamed.
> {
> if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
> return false;
>
>- while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0)
>- cpu_relax();
>+ /*
>+ * On hypervisors without PARAVIRT_SPINLOCKS support we fall
>+ * back to a Test-and-Set spinlock, because fair locks have
>+ * horrible lock 'holder' preemption issues.
>+ */
>+
This comment is also misleading... but if you tuck the whole function
under some PARAVIRT option, it obviously makes sense to just leave as is.
And let native actually _use_ qspinlocks.
>+ do {
>+ while (atomic_read(&lock->val) != 0)
>+ cpu_relax();
>+ } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0);
CCAS to the rescue again.
Thanks,
Davidlohr
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[4.2, Regression] Queued spinlocks cause major XFS performance regression Dave Chinner <david@fromorbit.com> - 2015-09-04 07:50 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-04 08:40 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Dave Chinner <david@fromorbit.com> - 2015-09-04 09:20 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Juergen Gross <jgross@suse.com> - 2015-09-04 09:40 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-04 10:00 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Dave Chinner <david@fromorbit.com> - 2015-09-04 10:40 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-04 17:10 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-04 17:20 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-04 17:30 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Dave Chinner <david@fromorbit.com> - 2015-09-07 01:40 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Davidlohr Bueso <dave@stgolabs.net> - 2015-09-07 02:10 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-07 09:00 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-07 22:50 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Davidlohr Bueso <dave@stgolabs.net> - 2015-09-08 08:40 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-08 12:10 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-08 19:50 +0200
[tip:locking/core] locking/qspinlock/x86: Fix performance regression under unaccelerated VMs tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2015-09-13 13:00 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-04 17:30 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-04 17:40 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-04 18:00 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Waiman Long <waiman.long@hpe.com> - 2015-09-10 04:20 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-04 18:00 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-05 19:50 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-04 09:40 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra <peterz@infradead.org> - 2015-09-04 13:40 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Dave Chinner <david@fromorbit.com> - 2015-09-05 00:10 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Dave Chinner <david@fromorbit.com> - 2015-09-07 01:50 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Waiman Long <waiman.long@hpe.com> - 2015-09-10 04:10 +0200
Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Waiman Long <waiman.long@hpe.com> - 2015-09-10 04:20 +0200
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