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

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Message-ID: <1364355032.6345.200.camel@gandalf.local.home>
Date:	Tue, 26 Mar 2013 23:30:32 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
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 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?

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

-- Steve


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