Re: [RFC] perf record: missing buildid for callstack modules

[Peter Zijlstra]

On Tue, Jan 12, 2016 at 11:38:05AM -0300, Arnaldo Carvalho de Melo wrote:
> > Also, just parsing the gigabytes of data that comes out of perf-record
> > takes significant time, let alone poking around the filesystem and
> 
> Right, that is what we would elliminate with stashing the content-based
> cookie into a PERF_RECORD_MMAP3 record.

Again, how would you go about getting that cookie for a DSO? The whole
kernel isn't involved with dlopen(), all it sees is a mmap(PROT_EXEC).

> BTW, mtime would incur in postprocessing it all.

mtime can still warn you if things are non-matching at report time
without this post-processing, and thereby solves the problem of staring
at broken/wrong data.

It doesn't get you right data, but knowing your data is broken allows
you to manually do things 'right'.