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Date: Thu, 02 Oct 2014 01:08:18 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Hemant Kumar <hemant@...ux.vnet.ibm.com>
Cc: linux-kernel@...r.kernel.org, srikar@...ux.vnet.ibm.com,
peterz@...radead.org, oleg@...hat.com,
hegdevasant@...ux.vnet.ibm.com, mingo@...hat.com, anton@...hat.com,
systemtap@...rceware.org, namhyung@...nel.org,
aravinda@...ux.vnet.ibm.com, penberg@....fi
Subject: Re: [PATCH v1 0/5] perf/sdt: SDT events listing/probing
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 ‘sdt_err’:
util/sdt.c:72:3: error: implicit declaration of function ‘pr_err’ [-Werror=implicit-function-declaration]
pr_err("%s: No SDT events found\n", target);
^
util/sdt.c:72:3: error: nested extern declaration of ‘pr_err’ [-Werror=nested-externs]
util/sdt.c: In function ‘file_hash_list__init’:
util/sdt.c:489:3: error: implicit declaration of function ‘pr_debug’ [-Werror=implicit-function-declaration]
pr_debug("Error in madvise\n");
^
util/sdt.c:489:3: error: nested extern declaration of ‘pr_debug’ [-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@...achi.com
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