From: Will Deacon <will.deacon@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <waiman.long@hpe.com>,
linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
manfred@colorfullife.com, dave@stgolabs.net,
paulmck@linux.vnet.ibm.com, boqun.feng@gmail.com, tj@kernel.org,
pablo@netfilter.org, kaber@trash.net, davem@davemloft.net,
oleg@redhat.com, netfilter-devel@vger.kernel.org,
sasha.levin@oracle.com, hofrat@osadl.org
Subject: Re: [PATCH -v3 7/8] locking: Move smp_cond_load_acquire() and friends into asm-generic/barrier.h
Date: Wed, 1 Jun 2016 15:07:14 +0100 [thread overview]
Message-ID: <20160601140713.GE355@arm.com> (raw)
In-Reply-To: <20160601124541.GS3190@twins.programming.kicks-ass.net>
On Wed, Jun 01, 2016 at 02:45:41PM +0200, Peter Zijlstra wrote:
> On Wed, Jun 01, 2016 at 01:13:33PM +0100, Will Deacon wrote:
> > On Wed, Jun 01, 2016 at 02:06:54PM +0200, Peter Zijlstra wrote:
>
> > > Works for me; but that would loose using cmpwait() for
> > > !smp_cond_load_acquire() spins, you fine with that?
> > >
> > > The two conversions in the patch were both !acquire spins.
> >
> > Maybe we could go the whole hog and add smp_cond_load_relaxed?
>
> What about say the cmpxchg loops in queued_write_lock_slowpath()
> ? Would that be something you'd like to use wfe for?
Without actually running the code on real hardware, it's hard to say
for sure. I notice that those loops are using cpu_relax_lowlatency
at present and we *know* that we're next in the queue (i.e. we're just
waiting for existing readers to drain), so the benefit of wfe is somewhat
questionable here and I don't think we'd want to add that initially.
Will
next prev parent reply other threads:[~2016-06-01 14:07 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-31 9:41 [PATCH -v3 0/8] spin_unlock_wait borkage and assorted bits Peter Zijlstra
2016-05-31 9:41 ` [PATCH -v3 1/8] locking: Replace smp_cond_acquire with smp_cond_load_acquire Peter Zijlstra
2016-05-31 9:41 ` [PATCH -v3 2/8] locking: Introduce cmpwait() Peter Zijlstra
2016-05-31 9:41 ` [PATCH -v3 3/8] locking: Introduce smp_acquire__after_ctrl_dep Peter Zijlstra
2016-06-01 13:52 ` Boqun Feng
2016-06-01 16:22 ` Peter Zijlstra
2016-06-01 23:19 ` Boqun Feng
2016-05-31 9:41 ` [PATCH -v3 4/8] locking, arch: Update spin_unlock_wait() Peter Zijlstra
2016-06-01 11:24 ` Will Deacon
2016-06-01 11:37 ` Peter Zijlstra
2016-05-31 9:41 ` [PATCH -v3 5/8] locking: Update spin_unlock_wait users Peter Zijlstra
2016-05-31 9:41 ` [PATCH -v3 6/8] locking,netfilter: Fix nf_conntrack_lock() Peter Zijlstra
2016-05-31 9:41 ` [PATCH -v3 7/8] locking: Move smp_cond_load_acquire() and friends into asm-generic/barrier.h Peter Zijlstra
2016-05-31 20:01 ` Waiman Long
2016-06-01 9:31 ` Peter Zijlstra
2016-06-01 12:00 ` Will Deacon
2016-06-01 12:06 ` Peter Zijlstra
2016-06-01 12:13 ` Will Deacon
2016-06-01 12:45 ` Peter Zijlstra
2016-06-01 14:07 ` Will Deacon [this message]
2016-06-01 17:13 ` Peter Zijlstra
2016-06-01 16:53 ` Waiman Long
2016-05-31 9:41 ` [PATCH -v3 8/8] locking, tile: Provide TILE specific smp_acquire__after_ctrl_dep Peter Zijlstra
2016-05-31 15:32 ` Chris Metcalf
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