linux-kernel - Re: [RFC][PATCH RT] rwsem_rt: Another (more sane) approach to mulit reader rt locks

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Message-ID: <1337705539.13348.81.camel@gandalf.stny.rr.com>
Date:	Tue, 22 May 2012 12:52:19 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	RT <linux-rt-users@...r.kernel.org>,
	Clark Williams <williams@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC][PATCH RT] rwsem_rt: Another (more sane) approach to mulit
 reader rt locks

On Tue, 2012-05-22 at 18:40 +0200, Thomas Gleixner wrote:

> > I'm all for benchmarks. But right now, making all readers pass through a
> > single mutex is a huge bottle neck for a lot of loads. Yes, they are
> > mostly Java loads, but for some strange reason, our customers seems to
> > like to run Java on our RT kernel :-p
> 
> I'm well aware that mmap_sem is a PITA but replacing one nightmare
> with the next one is not the best approach.

Perhaps we could just change the mmap_sem to use this approach. Create a
new type of rwsem/lock for -rt that we can be picky about.

Yeah, mmap_sem is a real PITA and it would be nice to have a solution
that can be used until we can convert it to an RCU lock.

-- Steve


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