Messages in this thread | | | Date | Wed, 1 Apr 2009 14:25:16 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] tracing/filters: add run-time field descriptions to TRACE_EVENT_FORMAT events |
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* Tom Zanussi <tzanussi@gmail.com> wrote:
> > Oh, do you know why these unfiltered event are disappearing? > > It's because of the way ring_buffer_discard() currently works - > the filtered events are still there in the ring buffer taking up > space; they just aren't visible in the output because the read > skips over them. > > So if there's a high volume of events being recorded, any given > event can be quickly overwritten before it has a chance to be > read, or it may have been read and appeared in the output, but > between the time it was read and the next cat, could easily have > been overwritten, and therefore 'disappears' on the next cat. > > It's really no different from the normal case where there is no > filtering in place - the same thing would happen but you wouldn't > notice whether a particular event was still there or not the next > time you cat'ed the file, because of the large volume of events > being displayed. It's just more apparent when most of the events > are discarded and invisible. > > At least that's my theory based on my understanding of how the > ring-buffer works...
Correct, and this needs to be fixed.
Ingo
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