On Wed, 2010-11-17 at 10:10 -0500, Steven Rostedt wrote:
quoted text
> 
> Right, the problem with filtering is what do we want to filter, and what
> about copying?
> 
> Currently, we copy the data into the buffer and then filter on that
> data. We could also easily filter on the parameters of the tracepoint,
> but sometimes those parameters do not match the final output (as the
> case with sched_switch). Do we copy the data into a separate "per cpu"
> temp buffer, and figure out the filter then? And if the filter is fine,
> then copy into the buffer. This obviously is slow, due to the multiple
> copies. We could do this only if the filtering is enabled.

Right, so what is the primary purpose of this filtering stuff? As it
stands it makes stuff terribly slow, so you add overhead but the win
(presumably) is less data output, is that a sane trade-off?

Most people I've heard -- both at LinuxCon.JP and LPC -- are asking for
lower overhead tracing (while at the same time demanding more features).

Who are actually using this and can they provide some input on this?

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