[PATCH 6/8] perf record: Do not save pathname in ./debug/.build-id directory for vmlinux

From: Namhyung Kim
Date: Mon Nov 03 2014 - 20:17:27 EST


When perf record finishes a session recording, it then pre-process
samples in order to write build-id info from actually used DSOs.
During this process it'll call map__load() for kernel map, and it ends
up calling dso__load_vmlinux_path() which replaces dso->long_name.

But this function checks kernel's build-id before searching vmlinux
path so it'll have the cryptic name which can be confusing to users IMHO.

This patch adds a flag to skip the build-id check during record, so
it'll have a vmlinux path for the kernel dso->long_name.

Before:
# perf record -va sleep 3
mmap size 528384B
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.196 MB perf.data (~8545 samples) ]
Looking at the vmlinux_path (7 entries long)
Using /home/namhyung/.debug/.build-id/f0/6e17aa50adf4d00b88925e03775de107611551 for symbols

After:
# perf record -va sleep 3
mmap size 528384B
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.193 MB perf.data (~8432 samples) ]
Looking at the vmlinux_path (7 entries long)
Using /lib/modules/3.16.4-1-ARCH/build/vmlinux for symbols

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
tools/perf/builtin-record.c | 11 +++++++++++
tools/perf/util/symbol.c | 11 ++++++-----
tools/perf/util/symbol.h | 1 +
3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 5091a27e6d28..582c4da155ea 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -200,6 +200,17 @@ static int process_buildids(struct record *rec)
if (size == 0)
return 0;

+ /*
+ * During this process, it'll load kernel map and replace the
+ * dso->long_name to a real pathname it found. In this case
+ * we prefer the vmlinux path like
+ * /lib/modules/3.16.4/build/vmlinux
+ *
+ * rather than build-id path (in debug directory).
+ * $HOME/.debug/.build-id/f0/6e17aa50adf4d00b88925e03775de107611551
+ */
+ symbol_conf.ignore_vmlinux_buildid = true;
+
return __perf_session__process_events(session, start,
size - start,
size, &build_id__mark_dso_hit_ops);
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index c69915c9d5bc..c24c5b83156c 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1511,12 +1511,10 @@ int dso__load_vmlinux_path(struct dso *dso, struct map *map,
symbol_filter_t filter)
{
int i, err = 0;
- char *filename;
+ char *filename = NULL;

- pr_debug("Looking at the vmlinux_path (%d entries long)\n",
- vmlinux_path__nr_entries + 1);
-
- filename = dso__build_id_filename(dso, NULL, 0);
+ if (!symbol_conf.ignore_vmlinux_buildid)
+ filename = dso__build_id_filename(dso, NULL, 0);
if (filename != NULL) {
err = dso__load_vmlinux(dso, map, filename, true, filter);
if (err > 0)
@@ -1524,6 +1522,9 @@ int dso__load_vmlinux_path(struct dso *dso, struct map *map,
free(filename);
}

+ pr_debug("Looking at the vmlinux_path (%d entries long)\n",
+ vmlinux_path__nr_entries + 1);
+
for (i = 0; i < vmlinux_path__nr_entries; ++i) {
err = dso__load_vmlinux(dso, map, vmlinux_path[i], false, filter);
if (err > 0)
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index eb2c19bf8d90..ded3ca7266de 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -105,6 +105,7 @@ struct symbol_conf {
unsigned short nr_events;
bool try_vmlinux_path,
ignore_vmlinux,
+ ignore_vmlinux_buildid,
show_kernel_path,
use_modules,
sort_by_name,
--
2.1.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/