On Sun, Oct 21, 2012 at 06:38:49PM +0200, Ingo Molnar wrote:
>
> * Jiri Olsa <jo...@redhat.com> wrote:
>
> > hi,
> > adding support to read sample values through the PERF_SAMPLE_READ
> > sample type. It's now possible to specify 'S' modifier for an event
> > and get its sample value by PERF_SAMPLE_READ.
> >
> > For group the 'S' modifier will enable sampling only for the leader
> > and read all the group member by PERF_SAMPLE_READ smple type with
> > PERF_FORMAT_GROUP read format.
> >
> > This patchset is based on group report patches by Namhyung Kim:
> > http://lwn.net/Articles/518569/
> >
> > Example:
> > (making sample on cycles, reading both cycles and cache-misses
> > by PERF_SAMPLE_READ/PERF_FORMAT_GROUP)
> >
> > # ./perf record -e '{cycles,cache-misses}:S' ls
> > ...
> >
> > # ./perf report --group --show-total-period --stdio
> > # ========
> > # captured on: Sat Oct 20 16:53:39 2012
> > ...
> > # group: {cycles,cache-misses}
> > # ========
> > #
> > # Samples: 86 of event 'anon group { cycles, cache-misses }'
> > # Event count (approx.): 34863674
> > #
> > # Overhead Period Command Shared Object
> > Symbol
> > # ................ ........................ ....... .................
> > ................................
>
> Might make sense to consider this column enumeration:
>
> #
> # cycles
> # | cache-misses
> # | |
> > # v v
> > #
> > 16.56% 19.47% 5773450 475 ls [kernel.kallsyms]
> > [k] native_sched_clock
> > 10.87% 0.74% 3789088 18 ls [kernel.kallsyms]
> > [k] rtl8169_interrupt
no problem in '--stdio' mode I guess.. not sure in '--tui/--gtk', Namhyung?
> > 9.82% 15.86% 3423364 387 ls [kernel.kallsyms]
> > [k] mark_lock
> > 8.43% 17.75% 2938384 433 ls ld-2.14.90.so
> > [.] do_lookup_x
> > 6.79% 20.86% 2365622 509 ls ls
> > [.] calculate_columns
> > 6.36% 0.61% 2216808 15 ls [kernel.kallsyms]
> > [k] lock_release
> > ...
>
> /me wants this feature ASAP :-)
>
> This should probably be the out of box default for perf record
> and perf top as well - the cache miss rate is probably one of
> the least appreciated aspects of overhead analysis.
>
> Does it have sane output if the cache-misses event is not
> supported? The cache-misses column should probably stay empty in
> that case - basically falling back to today's default output.
unsupported counters fail before report:
# ./perf record -e '{cycles,stalled-cycles-backend}:S' ls
Error:
The stalled-cycles-backend event is not supported.
ls: Terminated
similar for top, so we'd need special treatment for default
thanks,
jirka
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