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

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Date:	Wed, 3 Jan 2007 17:07:28 -0800
From:	Bill Huey (hui) <billh@...ppy.monkey.org>
To:	"Chen, Tim C" <tim.c.chen@...el.com>
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>,
	"Bill Huey (hui)" <billh@...ppy.monkey.org>
Subject: Re: [PATCH] lock stat for -rt 2.6.20-rc2-rt2.2.lock_stat.patch

On Wed, Jan 03, 2007 at 05:00:49PM -0800, Bill Huey wrote:
> On Wed, Jan 03, 2007 at 04:46:37PM -0800, Chen, Tim C wrote:
> > @contention events = 247149
> > @failure_events = 146
> > @lookup_failed_scope = 175
> > @lookup_failed_static = 43
> > @static_found = 16
> > [1, 113, 77 -- 32768, 0]            {tcp_init, net/ipv4/tcp.c, 2426}
> > [2, 759, 182 -- 1, 0]           	{lock_kernel, -, 0}
> > [13, 0, 7 -- 4, 0]              	{kmem_cache_free, -, 0}
> > [25, 3564, 9278 -- 1, 0]            {lock_timer_base, -, 0}
> > [56, 9528, 24552 -- 3, 0]           {init_timers_cpu, kernel/timer.c, 1842}
> > [471, 52845, 17682 -- 10448, 0]     {sock_lock_init, net/core/sock.c, 817}
> > [32251, 9024, 242 -- 256, 0]        {init, kernel/futex.c, 2781}
> > [173724, 11899638, 9886960 -- 11194, 0]         {mm_init, kernel/fork.c, 369}
> 
> Thanks, the numbers look a bit weird in that the first column should
> have a bigger number of events than that second column since it is a
> special case subset. Looking at the lock_stat_note() code should show
> that to be the case. Did you make a change to the output ?
> 
> I can't tell which are "steal", actively running or overall contention
> stats against the lock from your output.

Also, the output is weird in that the "contention_events" should be
a total of all of the events in the first three columns. Clearly the
number is wrong and I don't know if the text output was mangled or
if that's accurate and my code is buggy. I have yet to see it give
me data like that yet in my set up.

The fourth and fifth columns are the number of times this lock was
initialized inline by a function like spin_lock_init(). It might
have a correspondence to clone() calls.

bill

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