From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] tracing/function-graph-tracer: use the more lightweight local clock
Date: Thu, 05 Mar 2009 08:30:13 +0100 [thread overview]
Message-ID: <1236238213.5330.10111.camel@laptop> (raw)
In-Reply-To: <20090305011941.GA9821@nowhere>
On Thu, 2009-03-05 at 02:19 +0100, Frederic Weisbecker wrote:
> It takes 1 ms to execute while tracing.
> Considering my frequency is 250 Hz, it means 1/4 of the system is used
> on timer interrupt while tracing.
>
> For now the hang is fixed, but not the awful latency. And I'm just too frightened
> to test it on 1000 Hz.
>
> But I plan to add a kind of watchdog to check how many time we spent inside an
> interrupt while graph tracing.
> By checking this time against the current Hz value, I could decide to abort the tracing
> for all irq.
That would basically render the thing useless :-(
Is it specifically function_graph that is so expensive? If so, is that
because of the function exit hook?
next prev parent reply other threads:[~2009-03-05 7:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-05 0:49 [PATCH 2/2] tracing/function-graph-tracer: use the more lightweight local clock Frederic Weisbecker
2009-03-05 1:19 ` Frederic Weisbecker
2009-03-05 7:30 ` Peter Zijlstra [this message]
2009-03-05 8:46 ` Frederic Weisbecker
2009-03-05 10:56 ` Ingo Molnar
2009-03-05 11:16 ` Frederic Weisbecker
2009-03-05 11:56 ` Ingo Molnar
2009-03-05 14:01 ` Frederic Weisbecker
2009-03-05 14:22 ` Ingo Molnar
2009-03-05 11:03 ` [tip:tracing/function-graph-tracer] " Frederic Weisbecker
2009-03-05 11:04 ` [PATCH 2/2] " Ingo Molnar
2009-03-05 11:23 ` Frederic Weisbecker
2009-03-05 11:38 ` Ingo Molnar
2009-03-05 11:18 ` [tip:tracing/function-graph-tracer] " Frederic Weisbecker
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