From: Will Deacon <will.deacon@arm.com>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Waiman Long <waiman.long@hpe.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org,
linux-s390@vger.kernel.org, linux-arch@vger.kernel.org,
Davidlohr Bueso <dave@stgolabs.net>,
Jason Low <jason.low2@hp.com>, Dave Chinner <david@fromorbit.com>,
Scott J Norton <scott.norton@hpe.com>,
Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier
Date: Mon, 20 Jun 2016 08:59:00 +0100 [thread overview]
Message-ID: <20160620075900.GB29165@arm.com> (raw)
In-Reply-To: <20160618084620.GA24424@insomnia>
On Sat, Jun 18, 2016 at 04:46:20PM +0800, Boqun Feng wrote:
> On Fri, Jun 17, 2016 at 02:17:27PM -0400, Waiman Long wrote:
> > keep the xchg() function as it is or use smp_store_release(&next->locked,
> > 1). So which one is a better alternative for ARM or PPC?
> >
>
> For PPC, I think xchg_release() + smp_store_release() is better than the
> current code, because the former has two lwsync while the latter has two
> sync, and sync is quite expensive than lwsync on PPC.
>
> I need to leave the ARM part to Will ;-)
I doubt there's much in it, but xchg() has DMB + release, so xchg_release +
smp_store_release is probably slightly better for us too.
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon@arm.com>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Waiman Long <waiman.long@hpe.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org,
linux-s390@vger.kernel.org, linux-arch@vger.kernel.org,
Davidlohr Bueso <dave@stgolabs.net>,
Jason Low <jason.low2@hp.com>, Dave Chinner <david@fromorbit.com>,
Scott J Norton <scott.norton@hpe.com>,
Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier
Date: Mon, 20 Jun 2016 07:59:00 +0000 [thread overview]
Message-ID: <20160620075900.GB29165@arm.com> (raw)
In-Reply-To: <20160618084620.GA24424@insomnia>
On Sat, Jun 18, 2016 at 04:46:20PM +0800, Boqun Feng wrote:
> On Fri, Jun 17, 2016 at 02:17:27PM -0400, Waiman Long wrote:
> > keep the xchg() function as it is or use smp_store_release(&next->locked,
> > 1). So which one is a better alternative for ARM or PPC?
> >
>
> For PPC, I think xchg_release() + smp_store_release() is better than the
> current code, because the former has two lwsync while the latter has two
> sync, and sync is quite expensive than lwsync on PPC.
>
> I need to leave the ARM part to Will ;-)
I doubt there's much in it, but xchg() has DMB + release, so xchg_release +
smp_store_release is probably slightly better for us too.
Will
next prev parent reply other threads:[~2016-06-20 7:59 UTC|newest]
Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-14 22:48 [RFC PATCH-tip v2 0/6] locking/rwsem: Enable reader optimistic spinning Waiman Long
2016-06-14 22:48 ` Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Waiman Long
2016-06-14 22:48 ` Waiman Long
2016-06-15 8:04 ` Boqun Feng
2016-06-15 8:04 ` Boqun Feng
2016-06-15 17:18 ` Peter Zijlstra
2016-06-15 17:18 ` Peter Zijlstra
2016-06-15 19:01 ` Waiman Long
2016-06-15 19:01 ` Waiman Long
2016-06-15 19:01 ` Waiman Long
2016-06-16 2:19 ` Boqun Feng
2016-06-16 2:19 ` Boqun Feng
2016-06-16 10:16 ` Will Deacon
2016-06-16 10:16 ` Will Deacon
2016-06-16 21:35 ` Waiman Long
2016-06-16 21:35 ` Waiman Long
2016-06-16 21:35 ` Waiman Long
2016-06-17 0:48 ` Boqun Feng
2016-06-17 0:48 ` Boqun Feng
2016-06-17 15:26 ` Waiman Long
2016-06-17 15:26 ` Waiman Long
2016-06-17 15:26 ` Waiman Long
2016-06-17 15:45 ` Will Deacon
2016-06-17 15:45 ` Will Deacon
2016-06-17 18:17 ` Waiman Long
2016-06-17 18:17 ` Waiman Long
2016-06-17 18:17 ` Waiman Long
2016-06-18 8:46 ` Boqun Feng
2016-06-18 8:46 ` Boqun Feng
2016-06-20 7:59 ` Will Deacon [this message]
2016-06-20 7:59 ` Will Deacon
2016-06-15 16:56 ` Davidlohr Bueso
2016-06-15 16:56 ` Davidlohr Bueso
2016-06-15 17:12 ` Peter Zijlstra
2016-06-15 17:12 ` Peter Zijlstra
2016-06-15 18:27 ` Davidlohr Bueso
2016-06-15 18:27 ` Davidlohr Bueso
2016-06-15 18:40 ` Peter Zijlstra
2016-06-15 18:40 ` Peter Zijlstra
2016-06-15 18:56 ` Davidlohr Bueso
2016-06-15 18:56 ` Davidlohr Bueso
2016-06-17 1:11 ` Davidlohr Bueso
2016-06-17 1:11 ` Davidlohr Bueso
2016-06-17 14:28 ` Waiman Long
2016-06-17 14:28 ` Waiman Long
2016-06-17 14:28 ` Waiman Long
2016-06-17 16:29 ` Davidlohr Bueso
2016-06-17 16:29 ` Davidlohr Bueso
2016-06-17 16:46 ` Davidlohr Bueso
2016-06-17 16:46 ` Davidlohr Bueso
2016-06-15 19:08 ` Waiman Long
2016-06-15 19:08 ` Waiman Long
2016-06-15 19:08 ` Waiman Long
2016-06-15 20:04 ` Waiman Long
2016-06-15 20:04 ` Waiman Long
2016-06-15 20:04 ` Waiman Long
2016-06-15 21:59 ` Peter Zijlstra
2016-06-15 21:59 ` Peter Zijlstra
2016-06-14 22:48 ` [RFC PATCH-tip v2 2/6] locking/rwsem: Stop active read lock ASAP Waiman Long
2016-06-14 22:48 ` Waiman Long
2016-06-15 17:22 ` Peter Zijlstra
2016-06-15 17:22 ` Peter Zijlstra
2016-06-15 19:17 ` Waiman Long
2016-06-15 19:17 ` Waiman Long
2016-06-15 19:17 ` Waiman Long
2016-06-16 2:14 ` Davidlohr Bueso
2016-06-16 2:14 ` Davidlohr Bueso
2016-06-16 21:25 ` Waiman Long
2016-06-16 21:25 ` Waiman Long
2016-06-16 21:25 ` Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 3/6] locking/rwsem: Enable count-based spinning on reader Waiman Long
2016-06-14 22:48 ` Waiman Long
2016-06-15 17:38 ` Peter Zijlstra
2016-06-15 17:38 ` Peter Zijlstra
2016-06-15 19:28 ` Waiman Long
2016-06-15 19:28 ` Waiman Long
2016-06-15 19:28 ` Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 4/6] locking/rwsem: move down rwsem_down_read_failed function Waiman Long
2016-06-14 22:48 ` Waiman Long
2016-06-15 17:40 ` Peter Zijlstra
2016-06-15 17:40 ` Peter Zijlstra
2016-06-15 19:21 ` Waiman Long
2016-06-15 19:21 ` Waiman Long
2016-06-15 19:21 ` Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 5/6] locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation Waiman Long
2016-06-14 22:48 ` Waiman Long
2016-06-15 17:43 ` Peter Zijlstra
2016-06-15 17:43 ` Peter Zijlstra
2016-06-15 19:31 ` Waiman Long
2016-06-15 19:31 ` Waiman Long
2016-06-15 19:31 ` Waiman Long
2016-06-15 21:57 ` Peter Zijlstra
2016-06-15 21:57 ` Peter Zijlstra
2016-06-15 17:45 ` Peter Zijlstra
2016-06-15 17:45 ` Peter Zijlstra
2016-06-15 19:35 ` Waiman Long
2016-06-15 19:35 ` Waiman Long
2016-06-15 19:35 ` Waiman Long
2016-06-14 22:48 ` [RFC PATCH-tip v2 6/6] locking/rwsem: Enable spinning readers Waiman Long
2016-06-14 22:48 ` Waiman Long
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