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

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Message-ID: <20130327061351.GB17125@lge.com>
Date:	Wed, 27 Mar 2013 15:13:51 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Christoph Lameter <cl@...ux.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 Tue, Mar 26, 2013 at 11:30:32PM -0400, Steven Rostedt wrote:
> On Wed, 2013-03-27 at 11:59 +0900, Joonsoo Kim wrote:
> 
> > How about using spin_try_lock() in unfreeze_partials() and
> > using spin_lock_contented() in get_partial_node() to reduce latency?
> > IMHO, this doesn't make code more deterministic, but can maintain
> > a benefit of cpu partial page with tolerable latency.
> 
> And what do you do when you fail the try lock? Try again, or just break
> out?

Just break out.

> 
> We can run benchmarks, but I don't like playing games in -rt. It either
> is deterministic, or it isn't.

Okay.

> 
> -- Steve
> 
> 
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