linux-kernel - Re: [Patch 00/15] Reduce tracing payload size.

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Date:	Mon, 6 Dec 2010 15:58:52 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Ted Ts'o <tytso@....edu>, Andi Kleen <andi@...stfloor.org>,
	David Sharp <dhsharp@...gle.com>, rostedt@...dmis.org,
	linux-kernel@...r.kernel.org, mrubin@...gle.com
Subject: Re: [Patch 00/15] Reduce tracing payload size.

On Mon, Dec 06, 2010 at 08:56:37AM -0500, Ted Ts'o wrote:
> On Mon, Dec 06, 2010 at 02:22:00PM +0100, Andi Kleen wrote:
> > David Sharp <dhsharp@...gle.com> writes:
> > >
> > > These patches are just a start to shrinking the size of trace events. I am
> > > planning to also make small versions of trace events that are used when
> > > CONFIG_SMALL_TRACES is enabled. I'm also open to discussion of other ways to
> > > shrink event sizes.
> > 
> > Maybe the simplest would be to lzo them as they get logged?
> > I assume you already considered that?
> 
> The tracing subsystem is supposed to be extremely low-overhead.
> Compressiong the event log would add considerable CPU overhead.  If we

lzo as a rule of thumb is about as expensive as 3x memcpy()
That's not really expensive.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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