linux-kernel - Re: [RT LATENCY] 249 microsecond latency caused by slub's unfreeze

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Message-ID: <1365602951.9609.10.camel@gandalf.local.home>
Date:	Wed, 10 Apr 2013 10:09:11 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Pekka Enberg <penberg@...nel.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	LKML <linux-kernel@...r.kernel.org>,
	RT <linux-rt-users@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Clark Williams <clark@...hat.com>
Subject: Re: [RT LATENCY] 249 microsecond latency caused by slub's
 unfreeze_partials() code.

On Wed, 2013-04-10 at 14:00 +0000, Christoph Lameter wrote:
> On Wed, 10 Apr 2013, Joonsoo Kim wrote:
> 
> > > Christoph, Joonsoo, comments?
> >
> > Steven's comment is reasonable to me.
> >
> > If there is no objection from Christoph,
> > let's drop a patch in which I implement Christoph's idea.
> 
> Fine with me.
> 
> I do not like passing a reference just because we have to
> return an additional counter. Adds a lot of overhead.
> 

The reference is only passed to acquire_slab() which is a static inline
function that's only called by this function. You would think that gcc
can optimize that to remove the "lot of overhead".

-- Steve


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