From: Jason Low <jason.low2@hp.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@kernel.org>, Waiman Long <Waiman.Long@hp.com>,
Davidlohr Bueso <davidlohr@hp.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Rik van Riel <riel@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Anvin <hpa@zytor.com>, Andi Kleen <andi@firstfloor.org>,
Jej B <James.Bottomley@hansenpartnership.com>,
Steven Rostedt <rostedt@goodmis.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
"Chandramouleeswaran, Aswin" <aswin@hp.com>,
"Norton, Scott J" <scott.norton@hp.com>,
"Vinod, Chegu" <chegu_vinod@hp.com>
Subject: Re: [RFC] Cancellable MCS spinlock rework
Date: Thu, 03 Jul 2014 11:22:25 -0700 [thread overview]
Message-ID: <1404411745.8764.27.camel@j-VirtualBox> (raw)
In-Reply-To: <CA+55aFy=CnCLet=B9Q5dYU9w885sXNuYVDSkjHAp5V+nczbn3Q@mail.gmail.com>
On Thu, 2014-07-03 at 08:35 -0700, Linus Torvalds wrote:
> On Thu, Jul 3, 2014 at 8:31 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > I don't think we'll support 2 _billion_ processes/threads waiting on
> > the same semaphore any time soon, so the 'long' seems a bit of an
> > overkill on 64-bit architectures.
>
> Oh, never mind. The 'struct semaphore' uses it as just a plain count,
> but the rwsem ends up splitting up the bits for readers/writers, so we
> actually do want the full 64-bit value there.
Yeah, that was the key to reducing the struct size as the rwsem count
can't share a 64 bit chunk with the spinlock, unlike some of the other
lock.
Thanks,
Jason
next prev parent reply other threads:[~2014-07-03 18:22 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-02 16:21 [RFC] Cancellable MCS spinlock rework Jason Low
2014-07-02 16:27 ` Peter Zijlstra
2014-07-02 16:59 ` Jason Low
2014-07-02 17:23 ` Peter Zijlstra
2014-07-02 17:30 ` Jason Low
2014-07-03 4:39 ` Jason Low
2014-07-03 7:31 ` Peter Zijlstra
2014-07-03 15:31 ` Linus Torvalds
2014-07-03 15:35 ` Linus Torvalds
2014-07-03 18:22 ` Jason Low [this message]
2014-07-03 7:31 ` Peter Zijlstra
2014-07-03 17:09 ` Davidlohr Bueso
2014-07-03 18:34 ` Jason Low
2014-07-03 20:35 ` Waiman Long
2014-07-03 20:51 ` Jason Low
2014-07-03 21:35 ` Waiman Long
2014-07-03 21:54 ` Jason Low
2014-07-04 7:49 ` Peter Zijlstra
2014-07-04 1:07 ` Jason Low
2014-07-04 7:51 ` Peter Zijlstra
2014-07-07 17:22 ` Jason Low
2014-07-04 9:17 ` Peter Zijlstra
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