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author | Namhyung Kim <namhyung@kernel.org> | 2014-11-04 10:14:33 +0900 |
---|---|---|
committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2014-11-05 10:14:08 -0300 |
commit | b837a8bdc48925e6512412973b845c53cbe2b412 (patch) | |
tree | 4500fe49d11b079e963cd63d5fe8617fa4c88761 | |
parent | 00dc865798a31d3d5300dd5d70166a4a85f76a20 (diff) | |
download | linux-stable-b837a8bdc48925e6512412973b845c53cbe2b412.tar.gz linux-stable-b837a8bdc48925e6512412973b845c53cbe2b412.tar.bz2 linux-stable-b837a8bdc48925e6512412973b845c53cbe2b412.zip |
perf tools: Fix build-id matching on vmlinux
There's a problem on finding correct kernel symbols when perf report
runs on a different kernel. Although a part of the problem was solved
by the prior commit 0a7e6d1b6844 ("perf tools: Check recorded kernel
version when finding vmlinux"), there's a remaining problem still.
When perf records samples, it synthesizes the kernel map using
machine__mmap_name() and ref_reloc_sym like "[kernel.kallsyms]_text".
You can easily see it using 'perf report -D' command.
After finishing record, it goes through the recorded events to find
maps/dsos actually used. And then record build-id info of them.
During this process, it needs to load symbols in a dso and it'd call
dso__load_vmlinux_path() since the default value of the symbol_conf.
try_vmlinux_path is true. However it changes dso->long_name to a real
path of the vmlinux file (e.g. /lib/modules/3.16.4/build/vmlinux) if one
is running on a custom kernel.
It resulted in that perf report reads the build-id of the vmlinux, but
cannot use it since it only knows about the [kernel.kallsyms] map. It
then falls back to possible vmlinux paths by using the recorded kernel
version (in case of a recent version) or a running kernel silently.
Even with the recent tools, this still has a possibility of breaking
the result. As the build directory is a symbolic link, if one built a
new kernel in the same directory with different source/config, the old
link to vmlinux will point the new file. So it's absolutely needed to
use build-id when finding a kernel image.
In this patch, it's now changed to try to search a kernel dso in the
existing dso list which was constructed during build-id table parsing
so it'll always have a build-id. If not found, search "[kernel.kallsyms]".
Before:
$ perf report
# Children Self Command Shared Object Symbol
# ........ ........ ....... ................. ...............................
#
72.15% 0.00% swapper [kernel.kallsyms] [k] set_curr_task_rt
72.15% 0.00% swapper [kernel.kallsyms] [k] native_calibrate_tsc
72.15% 0.00% swapper [kernel.kallsyms] [k] tsc_refine_calibration_work
71.87% 71.87% swapper [kernel.kallsyms] [k] module_finalize
...
After (for the same perf.data):
72.15% 0.00% swapper vmlinux [k] cpu_startup_entry
72.15% 0.00% swapper vmlinux [k] arch_cpu_idle
72.15% 0.00% swapper vmlinux [k] default_idle
71.87% 71.87% swapper vmlinux [k] native_safe_halt
...
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/20140924073356.GB1962@gmail.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1415063674-17206-8-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-rw-r--r-- | tools/perf/util/header.c | 2 | ||||
-rw-r--r-- | tools/perf/util/machine.c | 16 |
2 files changed, 15 insertions, 3 deletions
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c index 3e2c156d9c64..76442caca37e 100644 --- a/tools/perf/util/header.c +++ b/tools/perf/util/header.c @@ -1269,7 +1269,7 @@ static int __event_process_build_id(struct build_id_event *bev, dso__set_build_id(dso, &bev->build_id); - if (filename[0] == '[') + if (!is_kernel_module(filename, NULL)) dso->kernel = dso_type; build_id__sprintf(dso->build_id, sizeof(dso->build_id), diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index 946c7d62cb6e..53f90e9c65fe 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -1085,8 +1085,20 @@ static int machine__process_kernel_mmap_event(struct machine *machine, * Should be there already, from the build-id table in * the header. */ - struct dso *kernel = __dsos__findnew(&machine->kernel_dsos, - kmmap_prefix); + struct dso *kernel = NULL; + struct dso *dso; + + list_for_each_entry(dso, &machine->kernel_dsos.head, node) { + if (is_kernel_module(dso->long_name, NULL)) + continue; + + kernel = dso; + break; + } + + if (kernel == NULL) + kernel = __dsos__findnew(&machine->kernel_dsos, + kmmap_prefix); if (kernel == NULL) goto out_problem; |