From: Will Deacon <will.deacon@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <waiman.long@hp.com>, Ingo Molnar <mingo@redhat.com>,
Arnd Bergmann <arnd@arndb.de>,
Thomas Gleixner <tglx@linutronix.de>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Scott J Norton <scott.norton@hp.com>,
Douglas Hatch <doug.hatch@hp.com>
Subject: Re: [PATCH 2/4] locking/qrwlock: Reduce reader/writer to reader lock transfer latency
Date: Wed, 8 Jul 2015 18:19:49 +0100 [thread overview]
Message-ID: <20150708171949.GE6348@arm.com> (raw)
In-Reply-To: <20150708095248.GZ3644@twins.programming.kicks-ass.net>
On Wed, Jul 08, 2015 at 10:52:48AM +0100, Peter Zijlstra wrote:
> On Tue, Jul 07, 2015 at 05:29:50PM -0400, Waiman Long wrote:
> > I prefer the current setting as you won't know if the writer has the
> > lock or not when you take a snapshot of the value of the lock. You
> > need the whole time sequence in this case to figure it out and so will
> > be more prone to error.
>
> I still need to wake up, but I suspect we need to change
> queue_read_{try,}lock() to use cmpxchg/inc_not_zero like things, which
> is fine for ARM, but not so much for x86.
>
> So I think I agree with Waiman, but am willing to be shown differently.
That's fine; I just wanted to make sure I wasn't going round the twist!
Will
next prev parent reply other threads:[~2015-07-08 17:19 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-06 15:43 [PATCH 0/4] locking/qrwlock: Improve qrwlock performance Waiman Long
2015-07-06 15:43 ` [PATCH 1/4] locking/qrwlock: Better optimization for interrupt context readers Waiman Long
2015-07-06 15:43 ` [PATCH 2/4] locking/qrwlock: Reduce reader/writer to reader lock transfer latency Waiman Long
2015-07-06 18:23 ` Will Deacon
2015-07-06 19:49 ` Waiman Long
2015-07-07 9:17 ` Will Deacon
2015-07-07 11:17 ` Peter Zijlstra
2015-07-07 11:49 ` Will Deacon
2015-07-07 14:30 ` Waiman Long
2015-07-07 17:27 ` Will Deacon
2015-07-07 18:10 ` Will Deacon
2015-07-07 21:29 ` Waiman Long
2015-07-08 9:52 ` Peter Zijlstra
2015-07-08 17:19 ` Will Deacon [this message]
2015-07-06 15:43 ` [PATCH 3/4] locking/qrwlock: Reduce writer to writer " Waiman Long
2015-07-06 15:43 ` [PATCH 4/4] locking/qrwlock: Use direct MCS lock/unlock in slowpath Waiman Long
2015-07-07 11:24 ` Peter Zijlstra
2015-07-07 21:59 ` Waiman Long
2015-07-07 22:13 ` Peter Zijlstra
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