linux-kernel - Re: [RFC patch 0/5] futex: Allow lockless empty check of hashbucket plist in futex

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Message-ID: <alpine.DEB.2.02.1311281523250.30673@ionos.tec.linutronix.de>
Date:	Thu, 28 Nov 2013 15:23:47 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Davidlohr Bueso <davidlohr@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jason Low <jason.low2@...com>, Ingo Molnar <mingo@...nel.org>,
	Darren Hart <dvhart@...ux.intel.com>,
	Mike Galbraith <efault@....de>, Jeff Mahoney <jeffm@...e.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Scott Norton <scott.norton@...com>,
	Tom Vaden <tom.vaden@...com>,
	Aswin Chandramouleeswaran <aswin@...com>,
	Waiman Long <Waiman.Long@...com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [RFC patch 0/5] futex: Allow lockless empty check of hashbucket
 plist in futex_wake()

On Thu, 28 Nov 2013, Peter Zijlstra wrote:

> On Wed, Nov 27, 2013 at 11:44:38PM -0800, Davidlohr Bueso wrote:
> > How about both enlarging the table _and_ aligning the buckets? As you
> > know, increasing the size of the table also benefits (particularly in
> > larger systems) in having more spinlocks. So we reduce the amount of
> > collisions and alleviate contention on the hb->lock. Btw, do you have
> > any particular concerns about the larger hash table patch? 
> 
> My only concern was the amount of #ifdef.
> 
> Wouldn't something like the below also work?

Definitely.

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