* 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
> 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.
Thanks,
Ingo
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