Messages in this thread | | | Date | Wed, 27 Nov 2013 11:41:44 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf timechart: dynamically determine event data offset |
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Em Wed, Nov 27, 2013 at 11:17:43PM +0900, Namhyung Kim escreveu: > 2013-11-27 (수), 10:44 -0300, Arnaldo Carvalho de Melo: > > Same signature, 32-bit, 64-bit userland, so whoever wrote timechart, Arjan, I > > think, made no mistakes at using the kernel exported interface, choosing the > > most efficient way to extract the data, casting to a struct.
> > Yeah, using the interface that searches for a field name to get the offset and > > then add it to a pointer to then cast to the type will allow maximum flexibility, > > but is not really efficient.
> > Doing that for something that is not performance critical (probably) as > > timechart probably is not a problem, but so is not a problem using the patch > > that does the cast after finding the offset of the first non-common field.
> I'm not sure how it affects the performance really.
Hey, everytime we need to get the value of a field when processing each tracepoint sample we need to do it via:
struct format_field *pevent_find_field(struct event_format *event, const char *name) { struct format_field *format;
for (format = event->format.fields; format; format = format->next) { if (strcmp(format->name, name) == 0) break; }
return format; }
I don't think this is optimal, no.
But yeah, for things that don't have performance needs, don't process that many samples and hey, machines are fast and cheap these days ;-)
> But in most cases, using the libtraceevent would be a better solution IMHO.
It is the one that gives the most flexibily to change the kernel exported tracepoint interface at will, yes. > > Having said that, I'll take the latest patch, using perf_evsel__intval et all, > > if Namhyung sees no further problems with it. > Okay, after a quick glance I don't see anymore issue. You can add my > Ack there.
Ok, thanks for checking!
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