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Re: [PATCH v1 0/5] perf/sdt: SDT events listing/probing
- From: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- To: Hemant Kumar <hemant at linux dot vnet dot ibm dot com>
- Cc: linux-kernel at vger dot kernel dot org, srikar at linux dot vnet dot ibm dot com, peterz at infradead dot org, oleg at redhat dot com, hegdevasant at linux dot vnet dot ibm dot com, mingo at redhat dot com, anton at redhat dot com, systemtap at sourceware dot org, namhyung at kernel dot org, aravinda at linux dot vnet dot ibm dot com, penberg at iki dot fi
- Date: Thu, 02 Oct 2014 01:08:18 +0900
- Subject: Re: [PATCH v1 0/5] perf/sdt: SDT events listing/probing
- Authentication-results: sourceware.org; auth=none
- References: <20140930152055 dot 6698 dot 82709 dot stgit at hemant-fedora>
Hi,
(2014/10/01 0:29), Hemant Kumar wrote:
> This patchset helps in listing dtrace style markers(SDT) present in user space
> applications through perf.
> Notes/markers are placed at important places by the
> developers. They have a negligible overhead when not enabled.
> We can enable them and probe at these places and find some important information
> like the arguments' values, etc.
>
> We have lots of applications which use SDT markers today, like:
> Postgresql, MySql, Mozilla, Perl, Python, Java, Ruby, libvirt, QEMU, glib
>
> To add SDT markers into user applications:
> We need to have this header sys/sdt.h present.
> sys/sdt.h used is version 3.
> If not present, install systemtap-sdt-devel package (for fedora-20).
>
> With this patchset,
> - Use perf sdt-cache --add to add SDT events to a cache.
> # perf sdt-cache --add ./user_app
>
> 4 SDT events added for /home/user/user_app!
>
> - Use perf sdt-cache --del to remove SDT events from the cache>
> # perf sdt-cache --del ./user_app
>
> 4 events removed for /home/user/user_app!
>
> - Dump the cache onto stdout using perf sdt-cache --dump:
> # perf sdt-cache --dump
> /home/user/user_app :
> %user_app:foo_start
> %user_app:fun_start
>
> - To probe and trace an SDT event :
> # perf record -e %user_app:foo_start -aR sleep 10
Looks great! :)
However, when I've tried to build, I got below errors..
CC util/sdt.o
util/sdt.c: In function âsdt_errâ:
util/sdt.c:72:3: error: implicit declaration of function âpr_errâ [-Werror=implicit-function-declaration]
pr_err("%s: No SDT events found\n", target);
^
util/sdt.c:72:3: error: nested extern declaration of âpr_errâ [-Werror=nested-externs]
util/sdt.c: In function âfile_hash_list__initâ:
util/sdt.c:489:3: error: implicit declaration of function âpr_debugâ [-Werror=implicit-function-declaration]
pr_debug("Error in madvise\n");
^
util/sdt.c:489:3: error: nested extern declaration of âpr_debugâ [-Werror=nested-externs]
cc1: all warnings being treated as errors
Perhaps, you might working on the old tree. Could you update it?
Thank you,
>
> The support for perf to sdt events has undergone a lot of changes since it was
> introduced. After a lot of discussions (https://lkml.org/lkml/2014/7/20/284), the
> patchset is subdivided for ease of review.
> Previously, a patchset supporting "perf list sdt" was posted, but it didn't make
> much sense since, only listing SDT events for an ELF won't help.
> This patchset aims at adding a sub-command "sdt-cache" to perf to manage a cache
> for management of the SDT events.
>
> This link shows an example of marker probing with Systemtap:
> https://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps
>
> This link provides important info regarding SDT notes:
> http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
>
> - Markers in binaries :
> These SDT markers are present in the ELF in the section named
> ".note.stapsdt".
> Here, the name of the marker, its provider, type, location, base
> address, semaphore address.
> We can retrieve these values using the members name_off and desc_off in
> Nhdr structure. If these are not enabled, they are present in the ELF as nop.
>
> Changes since last series :
> - Changed the entire (linked) list structure to hash lists to manage the SDT events.
> - Added a sub command "sdt-cache" to perf to manage SDT events in the system.
> - Added support to add and remove SDT events onto a cache.
> - Added support to "perf record" to probe and record the SDT events.
>
> TODO:
> - Add support to add most of the SDT events on a system to the cache.
> - Recognizing arguments and support to probe on them.
>
> ---
>
> Hemant Kumar (5):
> perf/sdt: ELF support for SDT
> perf/sdt: Add SDT events into a cache
> perf/sdt: Show SDT cache contents
> perf/sdt: Delete SDT events from cache
> perf/sdt: Add support to perf record to trace SDT events
>
>
> tools/perf/Makefile.perf | 3
> tools/perf/builtin-record.c | 21 +
> tools/perf/builtin-sdt-cache.c | 108 +++++
> tools/perf/builtin.h | 1
> tools/perf/perf.c | 1
> tools/perf/util/parse-events.c | 7
> tools/perf/util/parse-events.h | 7
> tools/perf/util/probe-event.c | 120 ++++-
> tools/perf/util/probe-event.h | 8
> tools/perf/util/probe-finder.c | 3
> tools/perf/util/sdt.c | 925 ++++++++++++++++++++++++++++++++++++++++
> tools/perf/util/sdt.h | 30 +
> tools/perf/util/symbol-elf.c | 207 +++++++++
> tools/perf/util/symbol.h | 21 +
> 14 files changed, 1440 insertions(+), 22 deletions(-)
> create mode 100644 tools/perf/builtin-sdt-cache.c
> create mode 100644 tools/perf/util/sdt.c
> create mode 100644 tools/perf/util/sdt.h
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com