linux/include/uapi
Adrian Hunter b9511cd761 perf/x86: Fix time_shift in perf_event_mmap_page
Commit:

  b20112edea ("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.

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.

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.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: b20112edea ("perf/x86: Improve accuracy of perf/sched clock")
Link: http://lkml.kernel.org/r/1445001845-13688-2-git-send-email-adrian.hunter@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-20 10:30:52 +02:00
..
asm-generic userfaultfd: register uapi generic syscall (aarch64) 2015-09-22 15:09:53 -07:00
drm uapi/drm/i915_drm.h: fix userspace compilation. 2015-09-02 16:26:58 +03:00
linux perf/x86: Fix time_shift in perf_event_mmap_page 2015-10-20 10:30:52 +02:00
misc cxl: Add alternate MMIO error handling 2015-08-18 19:34:43 +10:00
mtd
rdma IB/hfi1: Add PSM2 user space header to header_install 2015-09-03 15:29:52 -04:00
scsi cxlflash: Virtual LUN support 2015-08-26 18:05:39 -07:00
sound ASoC: Disable topology support for v4.2 2015-08-19 18:31:54 +02:00
video
xen xen/privcmd: Further s/MFN/GFN/ clean-up 2015-09-08 18:03:54 +01:00
Kbuild cxl: Add userspace header file 2014-10-08 20:15:57 +11:00