On 19/10/15 11:08, Ingo Molnar wrote: > > * Adrian Hunter <[email protected]> wrote: > >> Commit b20112edeadf ("perf/x86: Improve accuracy of perf/sched clock") >> allowed the time_shift value in perf_event_mmap_page to be as much >> as 32. Unfortunately the documented algorithms for using time_shift >> have it shifting an integer, whereas to work correctly with the value >> 32, the type must be u64. >> >> Fix by limiting the shift to 31 and adjusting the multiplier accordingly. >> >> Also update the documentation of perf_event_mmap_page so that new code >> based on it will be more future-proof. >> >> Fixes: b20112edeadf ("perf/x86: Improve accuracy of perf/sched clock") >> Signed-off-by: Adrian Hunter <[email protected]> > > Would be nice to point out via what symptoms the code misbehaves and how > users > notice.
In the case of perf tools, Intel PT decodes correctly but the timestamps that are output (for example by perf script) have lost 32-bits of granularity so they look like they are not changing at all. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
