Messages in this thread | | | Date | Thu, 3 Jun 2010 14:54:45 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: how to use perf annotate on the kernel |
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Em Thu, Jun 03, 2010 at 07:23:02PM +0200, Stephane Eranian escreveu: > Arnaldo, > > I am trying to understand how one is supposed > to use perf annotate to get sample correlations > with kernel symbols. > > I do: > > # perf record -a -e cycles:k dd if=/dev/zero of=/dev/null count=1000000 > # perf report > > # Events: 14K cycles > # > # Overhead Command Shared Object Symbol > # ........ ............... ................... ...... > # > 8.76% dd [kernel.kallsyms] [k] __lock_acquire > 7.49% dd [kernel.kallsyms] [k] sched_clock > > # perf annotate (or annotate -d '[kernel.kallsyms]'?) > Can't annotate __lock_acquire: No vmlinux file was found in the path > > # perf annotate -k vmlinux > objdump: '[kernel.kallsyms]': No such file
This looks like a bug in how it reports this problem, probably vmlinux is not in the current directory, or it is but has a build-id that doesn't matches the one in the perf.data file.
But the message is wrong, should be like it is in the tui, for this same situation:
ui_helpline__puts("No vmlinux file found, can't " "annotate with just a kallsyms file");
> Am I missing something here?
If you don't specify it with --vmlinux/-k it will try to find it in one of these places:
vmlinux_path[vmlinux_path__nr_entries] = strdup("vmlinux"); if (vmlinux_path[vmlinux_path__nr_entries] == NULL) goto out_fail; ++vmlinux_path__nr_entries; vmlinux_path[vmlinux_path__nr_entries] = strdup("/boot/vmlinux"); if (vmlinux_path[vmlinux_path__nr_entries] == NULL) goto out_fail; ++vmlinux_path__nr_entries; snprintf(bf, sizeof(bf), "/boot/vmlinux-%s", uts.release); vmlinux_path[vmlinux_path__nr_entries] = strdup(bf); if (vmlinux_path[vmlinux_path__nr_entries] == NULL) goto out_fail; ++vmlinux_path__nr_entries; snprintf(bf, sizeof(bf), "/lib/modules/%s/build/vmlinux", uts.release); vmlinux_path[vmlinux_path__nr_entries] = strdup(bf); if (vmlinux_path[vmlinux_path__nr_entries] == NULL) goto out_fail; ++vmlinux_path__nr_entries; snprintf(bf, sizeof(bf), "/usr/lib/debug/lib/modules/%s/vmlinux", uts.release); vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
It also now looks at /sys/kernel/notes, gets the build-id, and looks up in the build-id cache.
- Arnaldo
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