(2014/08/28 6:43), Hemant Kumar wrote: > The v3 patchset had some spacing errors because of my editor messing up during > sending the patches. Resending the patchset again. > 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-18). > > Please refer to the Documentation patch (3rd patch in this series) to see how > the > SDT markers are added into a program. > > With this patchset, > - Use perf to list the markers in the app: > # perf list sdt ./user_app > > ./user_app : > %user_app:foo_start > %user_app:fun_start > > This link shows an example of marker probing with Systemtap: > https://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps > > Also, this link provides important info regarding SDT notes: > http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation > > This patchset has undergone a lot of changes since it was first introduced. > Hence, the patchset has now been subdivided for more simplicity and ease of > review (thanks to the suggestion from Namhyung Kim). This contains the first 2 > of the 4 patches as suggested here: > https://lkml.org/lkml/2014/7/20/284
BTW, does this series only contain list command support? > - 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 : > - Subdivided the previous patchset into 4 patches to make it easier to review > as suggested by Namhyung Kim. (This set includes first two of the four > patches) > - Made the required changes and some optimizations suggested by Masami, > Namhyung > and Andi. > > TODO: > - Listing SDT events present in most of the binaries present in a system. > - Maintaining a cache of the SDT events for faster lookup. > - Add support to probe these SDT markers and integrate with a previous patch > (support to perf to probe SDT markers) posted in lkml. > https://lkml.org/lkml/2013/10/23/10 OK, I think we can postpone sdt-cache command, but this should go with probe-side improvements, because if perf-list shows sdt markers, users will be misled that the perf already supports sdt events. I'm OK if we hold this on a non-released branch on acme's tree. But it shouldn't be pushed to upstream without probe-side improvements. Arnaldo, would you think that works on your tree? Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
