From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] futex: lower the lock contention on the HB lock during wake up
Date: Sun, 21 Jun 2015 06:35:44 +0200 [thread overview]
Message-ID: <1434861344.6341.14.camel@gmail.com> (raw)
In-Reply-To: <558183FB.7060808@linutronix.de>
On Wed, 2015-06-17 at 16:28 +0200, Sebastian Andrzej Siewior wrote:
> On 06/17/2015 04:17 PM, Mike Galbraith wrote:
> > On Wed, 2015-06-17 at 10:33 +0200, Sebastian Andrzej Siewior wrote:
> >> wake_futex_pi() wakes the task before releasing the hash bucket lock
> >> (HB). The first thing the woken up task usually does is to acquire the
> >> lock which requires the HB lock. On SMP Systems this leads to blocking
> >> on the HB lock which is released by the owner shortly after.
> >> This patch rearranges the unlock path by first releasing the HB lock and
> >> then waking up the task.
> >>
> >> [bigeasy: redo ontop of lockless wake-queues]
> >> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> >> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> >
> > 4.1-rc8-rt4 contains this via 4.0-rt4, and seems fine on my 64 core
> > DL980. I ran a few iterations of futextests and stockfish, then mixed
> > two loops of futextest at different rt prios, with stockfish also rt,
> > and ltplight as tossed in as... crack filler. Box is still doing that,
> > is way too busy, but not griping about it.
>
> There are two patches mostly doing the same thing. The patch posted
> here is a redo ontop of "lockless wake-queues". It does hb-unlock,
> wakeup, de-boost. The patch merged into -RT is the original approach
> not using "lockless wake-queues" and performing wakeup, hb-unlock,
> de-boost.
>
> I plan to get into -RT the final solution once it hits upstream.
I plugged patch1 and tip version into rt and beat it, seems solid.
Converting the rest of rtmutex.c to use wake queues with ->save_state to
select wake function went less well. Kernel does a good impersonation
of a working kernel until I beat it up, then it loses wakeups. Hohum,
so much for yet another early morning tinker session.
-Mike
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next prev parent reply other threads:[~2015-06-21 4:35 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-19 17:24 [PATCH -tip 0/4] rtmutex: Spin on owner Davidlohr Bueso
2015-05-19 17:24 ` [PATCH 1/4] locking/rtmutex: Implement lockless top-waiter wakeup Davidlohr Bueso
2015-06-05 12:35 ` Thomas Gleixner
2015-06-16 19:29 ` [PATCH] futex: lower the lock contention on the HB lock during wake up Sebastian Andrzej Siewior
2015-06-16 19:50 ` Davidlohr Bueso
2015-06-17 8:33 ` [PATCH v2] " Sebastian Andrzej Siewior
2015-06-17 14:17 ` Mike Galbraith
2015-06-17 14:28 ` Sebastian Andrzej Siewior
2015-06-17 14:31 ` Mike Galbraith
2015-06-21 4:35 ` Mike Galbraith [this message]
2015-06-18 20:30 ` [tip:sched/core] futex: Lower " tip-bot for Sebastian Andrzej Siewior
2015-06-19 17:51 ` [PATCH v2] futex: lower " Kevin Hilman
2015-06-19 18:54 ` Thomas Gleixner
2015-06-19 19:32 ` Kevin Hilman
2015-06-19 19:33 ` [tip:sched/locking] futex: Lower " tip-bot for Sebastian Andrzej Siewior
2015-06-18 20:30 ` [tip:sched/core] locking/rtmutex: Implement lockless top-waiter wakeup tip-bot for Davidlohr Bueso
2015-05-19 17:24 ` [PATCH 2/4] locking/rtmutex: Use cmp-cmpxchg Davidlohr Bueso
2015-06-05 12:38 ` Thomas Gleixner
2015-06-06 15:27 ` Davidlohr Bueso
2015-06-15 18:34 ` Jason Low
2015-06-15 19:37 ` Davidlohr Bueso
2015-06-16 1:00 ` Jason Low
2015-05-19 17:24 ` [PATCH 3/4] locking/rtmutex: Update stale plist comments Davidlohr Bueso
2015-06-05 12:39 ` Thomas Gleixner
2015-06-18 20:57 ` [tip:sched/core] " tip-bot for Davidlohr Bueso
2015-06-19 19:33 ` [tip:sched/locking] " tip-bot for Davidlohr Bueso
2015-05-19 17:24 ` [PATCH -rfc 4/4] locking/rtmutex: Support spin on owner (osq) Davidlohr Bueso
2015-05-20 7:11 ` Paul Bolle
2015-05-25 20:35 ` Davidlohr Bueso
2015-05-29 15:19 ` Davidlohr Bueso
2015-05-29 18:01 ` Davidlohr Bueso
2015-06-05 13:59 ` Thomas Gleixner
2015-06-09 4:41 ` Davidlohr Bueso
2015-06-09 9:29 ` Thomas Gleixner
2015-06-09 11:21 ` Peter Zijlstra
2015-06-09 12:53 ` Thomas Gleixner
2015-05-25 20:35 ` [PATCH -tip 0/4] rtmutex: Spin on owner Davidlohr Bueso
2015-05-26 19:05 ` Thomas Gleixner
2015-09-15 1:26 [PATCH v2] futex: lower the lock contention on the HB lock during wake up Zhu Jefferry
2015-09-16 0:01 ` Thomas Gleixner
2015-09-16 0:17 ` Zhu Jefferry
2015-09-16 8:06 ` Thomas Gleixner
2015-09-16 9:52 ` Zhu Jefferry
2015-09-16 10:22 ` Thomas Gleixner
2015-09-16 11:13 ` Zhu Jefferry
2015-09-16 13:39 ` Thomas Gleixner
2015-09-16 23:57 ` Zhu Jefferry
2015-09-17 7:08 ` Thomas Gleixner
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