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SubjectRe: [PATCH] tracing/filters: add run-time field descriptions to TRACE_EVENT_FORMAT events

* 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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