Date: Sat, 23 Feb 2008 00:03:45 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Gregory Haskins <ghaskins@novell.com>, a.p.zijlstra@chello.nl,
       tglx@linutronix.de, rostedt@goodmis.org, linux-rt-users@vger.kernel.org,
       linux-kernel@vger.kernel.org, bill.huey@gmail.com, kevin@hilman.org,
       cminyard@mvista.com, dsingleton@mvista.com, dwalker@mvista.com,
       npiggin@suse.de, dsaxena@plexity.net, ak@suse.de, gregkh@suse.de,
       sdietrich@novell.com, pmorreale@novell.com, mkohari@novell.com
Subject: Re: [PATCH [RT] 00/14] RFC - adaptive real-time locks
Message-Id: <20080223000345.e6be3280.akpm@linux-foundation.org>
In-Reply-To: <20080221212420.GA20953@elte.hu>
References: <20080221152504.4804.8724.stgit@novell1.haskins.net>
	<20080221212420.GA20953@elte.hu>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1059
Lines: 22

On Thu, 21 Feb 2008 22:24:20 +0100 Ingo Molnar <mingo@elte.hu> wrote:

> regarding the concept: adaptive mutexes have been talked about in the 
> past, but their advantage is not at all clear, that's why we havent done 
> them. It's definitely not an unambigiously win-win concept.

When ext3 was converted from sleeping locks to spinlocks, dbench-on-numaq
throughput went up by a factor of ten.  I'd expect that what RT has done
was a truly awful change for lots of workloads on lots of machines.

Yeah, there's the dont-enable-it-if-you're-doing-that option, but that adds
the we-just-doubled-the-number-of-kernels-distros-need-to-ship problem.

Does -rt also make bit_spin_lock preemptible?  If not, I'd have thought the
change was of little benefit to ext3/jbd and it might as well go back to
spinning locks.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/