linux-kernel - Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning

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Message-ID: <alpine.DEB.1.10.0901071848431.23456@gandalf.stny.rr.com>
Date:	Wed, 7 Jan 2009 18:49:45 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	paulmck@...ux.vnet.ibm.com, Gregory Haskins <ghaskins@...ell.com>,
	Ingo Molnar <mingo@...e.hu>, Matthew Wilcox <matthew@....cx>,
	Andi Kleen <andi@...stfloor.org>,
	Chris Mason <chris.mason@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <npiggin@...e.de>,
	Peter Morreale <pmorreale@...ell.com>,
	Sven Dietrich <SDietrich@...ell.com>
Subject: Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning


On Wed, 7 Jan 2009, Linus Torvalds wrote:
> On Wed, 7 Jan 2009, Dave Kleikamp wrote:
> > 
> > Do you need to even do that if CONFIG_DEBUG_PAGEALLOC is unset?
> 
> No.
> 
> > Something like:
> > 
> > #ifdef CONFIG_DEBUG_PAGEALLOC
> >                 /*
> >                  * Need to access the cpu field knowing that
> >                  * DEBUG_PAGEALLOC could have unmapped it if
> >                  * the mutex owner just released it and exited.
> >                  */
> >                 if (probe_kernel_address(&thread->cpu, cpu))
> >                         break;
> > #else
> > 		cpu = thread->cpu;
> > #endif
> 
> yes. That would work fine.

What about memory hotplug as Ingo mentioned?

Should that be:

#if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_MEMORY_HOTPLUG)

??

-- Steve

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