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SubjectRe: [Patch 00/15] Reduce tracing payload size.
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On Mon, 2010-12-06 at 15:58 +0100, Andi Kleen wrote:
> 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@google.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.

Usually the most expensive thing in the trace is the memcpy(). Which is
why we try to do it only once.

-- Steve




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