Re: [RFC PATCH perf/core v2 00/16] perf-probe --cache and SDT support

[Hemant Kumar <hemant@linux.vnet.ibm.com>]

Hi Masami,

On 07/15/2015 02:43 PM, Masami Hiramatsu wrote:
> Hi,
>
> Here is the 2nd version of the patchset for probe-cache and
> initial SDT support which are going to be perf-cache finally.

Thanks for adding the SDT support.

> The perf-probe is useful for debugging, but it strongly depends
> on the debuginfo. Without debuginfo, it is just a frontend of
> ftrace's dynamic events. This can usually happen in server
> farms or on cloud system, since no one wants to distribute
> big debuginfo packages.
>
> To solve this issue, I had tried to make a pre-analyzed probes
> ( https://lkml.org/lkml/2014/10/31/207 ) but it has a problm
> that we can't ensure the probed binary is same as what we analyzed.
> Arnaldo gave me an idea to reuse build-id cache for that perpose
> and this series is the first prototype of that.
>
> At the same time, Hemant has started to support SDT probes which
> also use the cache file of SDT info. So I decided to merge this
> into the same build-id cache.
> In this version, SDT support is still very limited, it works
> as a part of probe-cache.
>
> In this version, perf probe supports --cache option which means
> that perf probe manipulate probe caches, for example,
>
>    # perf probe --cache --add "probe-desc"
>
> does not only add probe events but also add "probe-desc" and
> it's result on the cache. (Note that the cached entry is always
> referred even without --cache)
> The --list and --del commands also support --cache. Note that
> both are only manipulate caches, not real events.
>
> To use SDT, we have to scan the target binary at first by using
> perf-buildid-cache, e.g.
>
>    # perf buildid-cache --add /lib/libc-2.17.so
>
> And perf probe --cache --list shows what SDTs are scanned.
>
>    # perf probe --cache --list
>    /usr/lib/libc-2.17.so (a6fb821bdf53660eb2c29f778757aef294d3d392):
>    libc:setjmp=setjmp
>    libc:longjmp=longjmp
>    libc:longjmp_target=longjmp_target
>    libc:memory_heap_new=memory_heap_new
>    libc:memory_sbrk_less=memory_sbrk_less
>    libc:memory_arena_reuse_free_list=memory_arena_reuse_free_list
>    libc:memory_arena_reuse=memory_arena_reuse
>    ...
>
> To use the SDT events, perf probe -x BIN %SDTEVENT allows you to
> add a probe on SDTEVENT@BIN.
>
>    # perf probe -x /lib/libc-2.17.so %memory_heap_new
>
> If you define a cached probe with event name, you can also reuse
> it as same as SDT events.
>
>    # perf probe -x ./perf --cache -n 'myevent=dso__load $params'
>
> (Note that "-n" option only updates caches)
> To use the above "myevent", you just have to add "%myevent".
>
>    # perf probe -x ./perf %myevent
>
>
> TODOs:
>   - Show available cached/SDT events by perf-list
>   - Allow perf-record to use cached/SDT events directly

As I was already working on SDT events' recording
https://lkml.org/lkml/2014/11/2/73,
I can re-spin the patches on top of your patchset and make the
required changes to implement the above TODOs.
What would you suggest?

> Thank you,
>
> ---
>
> Hemant Kumar (1):
>        perf/sdt: ELF support for SDT
>
> Masami Hiramatsu (15):
>        perf probe: Simplify __add_probe_trace_events code
>        perf probe: Move ftrace probe-event operations to probe-file.c
>        perf probe: Use strbuf for making strings in probe-event.c
>        perf-buildid-cache: Use path/to/bin/buildid/elf instead of path/to/bin/buildid
>        perf buildid: Use SBUILD_ID_SIZE macro
>        perf buildid: Introduce sysfs/filename__sprintf_build_id
>        perf: Add lsdir to read a directory
>        perf-buildid-cache: Use lsdir for looking up buildid caches
>        perf probe: Add --cache option to cache the probe definitions
>        perf probe: Use cache entry if possible
>        perf probe: Show all cached probes
>        perf probe: Remove caches when --cache is given
>        perf probe: Add group name support
>        perf buildid-cache: Scan and import user SDT events to probe cache
>        perf probe: Accept %sdt and %cached event name
>
>
>   tools/perf/Documentation/perf-probe.txt |   14
>   tools/perf/builtin-buildid-cache.c      |   22 -
>   tools/perf/builtin-buildid-list.c       |   28 -
>   tools/perf/builtin-probe.c              |    3
>   tools/perf/util/Build                   |    1
>   tools/perf/util/build-id.c              |  230 ++++++--
>   tools/perf/util/build-id.h              |   11
>   tools/perf/util/dso.h                   |    5
>   tools/perf/util/probe-event.c           |  918 ++++++++++++++-----------------
>   tools/perf/util/probe-event.h           |   16 -
>   tools/perf/util/probe-file.c            |  763 ++++++++++++++++++++++++++
>   tools/perf/util/probe-file.h            |   46 ++
>   tools/perf/util/probe-finder.c          |   10
>   tools/perf/util/symbol-elf.c            |  252 +++++++++
>   tools/perf/util/symbol.c                |    2
>   tools/perf/util/symbol.h                |   22 +
>   tools/perf/util/util.c                  |   34 +
>   tools/perf/util/util.h                  |    4
>   18 files changed, 1781 insertions(+), 600 deletions(-)
>   create mode 100644 tools/perf/util/probe-file.c
>   create mode 100644 tools/perf/util/probe-file.h
>
>

-- 
Thanks,
Hemant Kumar