Messages in this thread | | | Date | Thu, 5 Nov 2009 09:27:33 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/1] perf symbols: Use the buildids if present |
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* Masami Hiramatsu <mhiramat@redhat.com> wrote:
> Arnaldo Carvalho de Melo wrote: >> From: Arnaldo Carvalho de Melo<acme@redhat.com> >> >> Now 'perf record' will intercept PERF_RECORD_MMAP calls, creating a >> linked list of DSOs, then when the session finishes, it will traverse >> this list and read the buildids, stashing them at the end of the file >> and will set up a new feature bit in the header bitmask. >> >> 'perf report' will then notice this feature and populate the 'dsos' list >> and set the build ids. >> >> When reading the symtabs it will refuse to load from a file that doesn't >> have the same build id. >> >> Example: >> >> [root@doppio ~]# perf report | head >> /home/acme/bin/perf with build id b1ea544ac3746e7538972548a09aadecc5753868 not found, continuing without symbols >> # Samples: 2621434559 >> # >> # Overhead Command Shared Object Symbol >> # ........ ............... ............................. ...... >> # >> 7.91% init [kernel] [k] read_hpet >> 7.64% init [kernel] [k] mwait_idle_with_hints >> 7.60% swapper [kernel] [k] read_hpet >> 7.60% swapper [kernel] [k] mwait_idle_with_hints >> 3.65% init [kernel] [k] 0xffffffffa02339d9 >> [root@doppio ~]# >> >> In this case the 'perf' binary was an older one, vanished, so it the symbols >> probably wouldn't match. >> >> Next patches will support the kernel as well, reading the build id notes for it >> and the modules from /sys. > > Great! then I can use it on 'perf probe' to check the dwarf binary is > same as running kernel. > >> Another patch should also introduce a new plumbing command: >> >> 'perf list-buildids' >> >> that will then be used in porcelain that is distro specific to >> fetch -debuginfo packages where such buildids are present. This will in turn >> allow for one to run 'perf record' in one machine and 'perf report' in another. > > Hmm, so, will this command list up all debuginfo files with buildids? > If so, can it also find a kernel binary built locally?
Arnaldo, how about adding the kernel binary's build path to /sys/kernel/notes, during the kernel build? (With perhaps a .config override as well, for package builds.)
That object might or might not exist, and if it does not exist, or if there is a buildid mismatch, we can fall back to 'well known' places for kernel/module binaries.
Ingo
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