linux-kernel - Re: [PATCH 3/5] trace: Add per

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Message-ID: <1311974707.21143.93.camel@gandalf.stny.rr.com>
Date:	Fri, 29 Jul 2011 17:25:07 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Vaibhav Nagarnaik <vnagarnaik@...gle.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Michael Rubin <mrubin@...gle.com>,
	David Sharp <dhsharp@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] trace: Add per_cpu ring buffer control files

On Fri, 2011-07-29 at 12:13 -0700, Vaibhav Nagarnaik wrote:
> On Fri, Jul 29, 2011 at 11:14 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> > On Tue, 2011-07-26 at 15:59 -0700, Vaibhav Nagarnaik wrote:
> >> Add a debugfs entry under per_cpu/ folder for each cpu called
> >> buffer_size_kb to control the ring buffer size for each CPU
> >> independently.
> >>
> >> If the global file buffer_size_kb is used to set size, the individual
> >> ring buffers will be adjusted to the given size. The buffer_size_kb will
> >> report the common size to maintain backward compatibility.
> >>
> >> If the buffer_size_kb file under the per_cpu/ directory is used to
> >> change buffer size for a specific CPU, only the size of the respective
> >> ring buffer is updated. When tracing/buffer_size_kb is read, it reports
> >> the ring buffer sizes of all the CPUs at that point.
> >
> > No, buffer_size_kb should not change in the what it reports. This is why
> > you have a buffer_total_size_kb. Use that. If the per_cpu buffers are
> > changed, then this should just report "various" or something to that
> > affect. This will be a good way to know if the per_cpu buffers are the
> > same or not.
> 
> Aargh.
> 
> I updated the code to return 'X' when individual cpu buffers don't match
> up in size and forgot to update the changelog, I will do it now.
> 

Heh, I only looked at the changelog. I was going to say 'X' but then
thought that 'various' would be good too. But since we already use 'X'
for the filters and enabled files, it is better to stay consistent. So
'X' is fine.

-- Steve


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