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Groups > linux.kernel > #1310418
| From | Arnaldo Carvalho de Melo <acme@kernel.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [RFC] perf record: missing buildid for callstack modules |
| Date | 2016-01-15 20:50 +0100 |
| Message-ID | <qRixJ-2cl-33@gated-at.bofh.it> (permalink) |
| References | (5 earlier) <qQOgi-6eV-13@gated-at.bofh.it> <qQOpX-6iM-1@gated-at.bofh.it> <qR1Qe-7rW-7@gated-at.bofh.it> <qR91p-49P-27@gated-at.bofh.it> <qRhLk-1DX-13@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Em Fri, Jan 15, 2016 at 10:58:48AM -0800, Stephane Eranian escreveu:
> On Fri, Jan 15, 2016 at 1:34 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Thu, Jan 14, 2016 at 05:59:48PM -0800, Stephane Eranian wrote:
> >> Peter,
> >>
> >> On Thu, Jan 14, 2016 at 3:36 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >> > On Thu, Jan 14, 2016 at 12:27:34PM +0100, Ingo Molnar wrote:
> >> >> > + * u32 filename_len;
> >> >> > + * char filename[2+];
> >> >
> >> >> Acked-by: Ingo Molnar <mingo@kernel.org>
> >> >
> >> > except of course that sizeof(u32) == 4 :/
> >
> >> There is no padding here. Are you concerned about running out of bits
> >> in filename_len?
> >
> > No, I just made a mess of it :-)
> >
> > filename_len should have been u16 and filename should then be 6+8n in
> > size.
> >
> why don't you make it more explicit:
> u16 filename_len
> u16 extra_len
> then it would be clear what is what, no field with dual meaning.
> Now, that assumes that no pathname can be longer than 65535 bytes.
There is no requirement for the filename to start at a u64 boundary,
right? So it can start right after the filename_len, be it u16 or u32,
and that extra_len can be computed as Peter described right here:
> >> Any extension possible because header.size - sizeof(mmap3) -
> >> filename_len sizing what's after filename, right?
So, no need to have that extra_len :-)
Ah PATH_MAX is 4096, so I guess u16 should be enough, no?
- Arnaldo
> > Right, current MMAP records use the remaining size as the filename
> > length, but by explicitly specifying that we can add optional fields.
> >
> > These fields must be after filename_len, otherwise you'd not be able to
> > find filename_len and you could not compute the extra size. And given
> > alignment constraints it makes sense to do it after filename[].
> >
> > So suppose we wanted to also add atime and ctime, we could do.
> >
> > PERF_RECORD_MMAP3 {
> > ...
> > u16 filename_len;
> > char filename[6+8n];
> >
> > if (extra_size >= 16) {
> > u64 stime;
> > u64 ctime;
> > };
> > }
> >
> > or something like that.
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Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-07 23:00 +0100
Re: [RFC] perf record: missing buildid for callstack modules Stephane Eranian <eranian@google.com> - 2016-01-07 23:10 +0100
Re: [RFC] perf record: missing buildid for callstack modules Namhyung Kim <namhyung@gmail.com> - 2016-01-08 00:30 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-08 00:50 +0100
Re: [RFC] perf record: missing buildid for callstack modules Stephane Eranian <eranian@google.com> - 2016-01-08 19:10 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-08 19:20 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-11 18:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-11 19:30 +0100
Re: [RFC] perf record: missing buildid for callstack modules Stephane Eranian <eranian@google.com> - 2016-01-11 21:10 +0100
Re: [RFC] perf record: missing buildid for callstack modules Ingo Molnar <mingo@kernel.org> - 2016-01-12 11:50 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-12 12:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Ingo Molnar <mingo@kernel.org> - 2016-01-12 13:20 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-12 14:50 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-12 15:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-12 16:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-12 16:50 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-12 17:20 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-12 17:30 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-12 18:20 +0100
Re: [RFC] perf record: missing buildid for callstack modules Ingo Molnar <mingo@kernel.org> - 2016-01-13 11:30 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-13 13:50 +0100
Re: [RFC] perf record: missing buildid for callstack modules Ingo Molnar <mingo@kernel.org> - 2016-01-14 12:30 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-14 12:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Stephane Eranian <eranian@google.com> - 2016-01-15 03:00 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-15 10:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Stephane Eranian <eranian@google.com> - 2016-01-15 20:00 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-15 20:50 +0100
Re: [RFC] perf record: missing buildid for callstack modules Stephane Eranian <eranian@google.com> - 2016-01-15 22:50 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-15 22:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Stephane Eranian <eranian@google.com> - 2016-01-12 22:10 +0100
Re: [RFC] perf record: missing buildid for callstack modules One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-01-12 14:10 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-12 15:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-12 16:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Ingo Molnar <mingo@kernel.org> - 2016-01-13 11:30 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-12 15:30 +0100
Re: [RFC] perf record: missing buildid for callstack modules Ingo Molnar <mingo@kernel.org> - 2016-01-13 11:00 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-13 16:30 +0100
Re: [RFC] perf record: missing buildid for callstack modules Namhyung Kim <namhyung@kernel.org> - 2016-01-19 16:00 +0100
Re: [RFC] perf record: missing buildid for callstack modules Peter Zijlstra <peterz@infradead.org> - 2016-01-19 16:30 +0100
Re: [RFC] perf record: missing buildid for callstack modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-01-19 16:50 +0100
Re: [RFC] perf record: missing buildid for callstack modules Namhyung Kim <namhyung@kernel.org> - 2016-01-09 11:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Adrian Hunter <adrian.hunter@intel.com> - 2016-01-11 10:40 +0100
Re: [RFC] perf record: missing buildid for callstack modules Namhyung Kim <namhyung@kernel.org> - 2016-01-11 12:10 +0100
Re: [RFC] perf record: missing buildid for callstack modules Adrian Hunter <adrian.hunter@intel.com> - 2016-01-11 13:00 +0100
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