linux-kernel - RE: [PATCH] lock stat for -rt 2.6.20-rc2-rt2.2.lock

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Date:	Wed, 3 Jan 2007 16:25:46 -0800
From:	"Chen, Tim C" <tim.c.chen@...el.com>
To:	"Bill Huey \(hui\)" <billh@...ppy.monkey.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>, <linux-kernel@...r.kernel.org>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Steven Rostedt" <rostedt@...dmis.org>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Daniel Walker" <dwalker@...sta.com>
Subject: RE: [PATCH] lock stat for -rt 2.6.20-rc2-rt2.2.lock_stat.patch

Bill Huey (hui) wrote:
> 
> Good to know that. What did the output reveal ?
> 
> What's your intended use again summarized ? futex contention ? I'll
> read the first posting again.
> 

Earlier I used latency_trace and figured that there was read contention
on mm->mmap_sem during call to _rt_down_read by java threads
when I was running volanomark.  That caused the slowdown of the rt
kernel
compared to non-rt kernel.  The output from lock_stat confirm
that mm->map_sem was indeed the most heavily contended lock.

Tim
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