2013-11-27 (수), 11:41 -0300, Arnaldo Carvalho de Melo:
> 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 ;-)
Right. What I wanted to say actually was like s/how/how much/. :)
Thanks,
Namhyung
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