From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Daniel Walker <dwalker@mvista.com>
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>, Bill Huey <billh@gnuppy.monkey.org>,
Jason Baron <jbaron@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 3/5] lockstat: core infrastructure
Date: Wed, 30 May 2007 15:03:26 +0200 [thread overview]
Message-ID: <1180530206.7348.83.camel@twins> (raw)
In-Reply-To: <1180470525.32594.71.camel@imap.mvista.com>
On Tue, 2007-05-29 at 13:28 -0700, Daniel Walker wrote:
> On Tue, 2007-05-29 at 14:52 +0200, Peter Zijlstra wrote:
> > + now = sched_clock();
> > + waittime = now - hlock->waittime_stamp;
> > +
>
> It looks like your using sched_clock() through out .. It's a little
> troubling considering the constraints on the function .. Most
> architecture implement a jiffies sched_clock() w/ 1 millisecond or worse
> resolution.. I'd imagine a millisecond hold time is pretty rare, even a
> millisecond wait time might be fairly rare too .. There's also no
> guarantee that sched_clock timestamps off two different cpu's can be
> compared (or at least that's my understanding) ..
All valid points, however.. calling anything more expensive 2-3 times
per lock acquisition is going to be _very_ painful.
Also, IMHO the contention count vs the acquisition count is the most
interesting number, the times are just a nice bonus (if and when they
work).
next prev parent reply other threads:[~2007-05-30 13:19 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-29 12:52 [PATCH 0/5] lock contention tracking -v3 Peter Zijlstra
2007-05-29 12:52 ` [PATCH 1/5] fix raw_spinlock_t vs lockdep Peter Zijlstra
2007-05-29 12:52 ` [PATCH 2/5] lockdep: sanitise CONFIG_PROVE_LOCKING Peter Zijlstra
2007-05-29 13:21 ` Christoph Hellwig
2007-05-29 14:16 ` Ingo Molnar
2007-05-30 3:14 ` Andrew Morton
2007-05-29 12:52 ` [PATCH 3/5] lockstat: core infrastructure Peter Zijlstra
2007-05-29 20:28 ` Daniel Walker
2007-05-30 13:03 ` Peter Zijlstra [this message]
2007-05-30 13:24 ` Ingo Molnar
2007-05-30 13:40 ` Steven Rostedt
2007-05-30 13:49 ` Ingo Molnar
2007-05-30 17:06 ` Daniel Walker
2007-05-30 17:16 ` Peter Zijlstra
2007-05-30 17:25 ` Daniel Walker
2007-06-01 13:12 ` Ingo Molnar
2007-06-01 15:26 ` Daniel Walker
2007-06-01 15:52 ` Peter Zijlstra
2007-06-01 16:11 ` Daniel Walker
2007-06-01 18:30 ` Ingo Molnar
2007-06-01 19:25 ` Matt Mackall
2007-06-01 19:30 ` Daniel Walker
2007-06-01 18:43 ` Peter Zijlstra
2007-06-01 18:51 ` Ingo Molnar
2007-06-01 19:30 ` Daniel Walker
2007-06-01 18:19 ` Ingo Molnar
2007-06-01 19:30 ` Daniel Walker
2007-06-01 14:25 ` Andi Kleen
2007-05-30 15:20 ` Daniel Walker
2007-05-30 3:43 ` Andrew Morton
2007-05-29 12:52 ` [PATCH 4/5] lockstat: human readability tweaks Peter Zijlstra
2007-05-29 12:52 ` [PATCH 5/5] lockstat: hook into spinlock_t, rwlock_t, rwsem and mutex Peter Zijlstra
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