perf callchain: Cache eh/debug frame offset for dwarf unwind

When libunwind tries to resolve callchains it needs to know the offset
of .eh_frame_hdr or .debug_frame to access the dso.

Since it will always return the same result for a given DSO, just cache
the result as an optimization.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1422518843-25818-41-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 21 insertions, 11 deletions

diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 3782c82c6e44..ced92841ff97 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -139,6 +139,7 @@ struct dso {
                 u32              status_seen;
                 size_t           file_size;
                 struct list_head open_entry;
+                u64              frame_offset;
         } data;
 
         union { /* Tool specific area */
diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
index 6edf535f65c2..e3c40a520a25 100644
--- a/tools/perf/util/unwind-libunwind.c
+++ b/tools/perf/util/unwind-libunwind.c
@@ -266,14 +266,17 @@ static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
                                      u64 *fde_count)
 {
         int ret = -EINVAL, fd;
-        u64 offset;
+        u64 offset = dso->data.frame_offset;
 
-        fd = dso__data_fd(dso, machine);
-        if (fd < 0)
-                return -EINVAL;
+        if (offset == 0) {
+                fd = dso__data_fd(dso, machine);
+                if (fd < 0)
+                        return -EINVAL;
 
-        /* Check the .eh_frame section for unwinding info */
-        offset = elf_section_offset(fd, ".eh_frame_hdr");
+                /* Check the .eh_frame section for unwinding info */
+                offset = elf_section_offset(fd, ".eh_frame_hdr");
+                dso->data.frame_offset = offset;
+        }
 
         if (offset)
                 ret = unwind_spec_ehframe(dso, machine, offset,
@@ -287,14 +290,20 @@ static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
 static int read_unwind_spec_debug_frame(struct dso *dso,
                                         struct machine *machine, u64 *offset)
 {
-        int fd = dso__data_fd(dso, machine);
+        int fd;
+        u64 ofs = dso->data.frame_offset;
 
-        if (fd < 0)
-                return -EINVAL;
+        if (ofs == 0) {
+                fd = dso__data_fd(dso, machine);
+                if (fd < 0)
+                        return -EINVAL;
 
-        /* Check the .debug_frame section for unwinding info */
-        *offset = elf_section_offset(fd, ".debug_frame");
+                /* Check the .debug_frame section for unwinding info */
+                ofs = elf_section_offset(fd, ".debug_frame");
+                dso->data.frame_offset = ofs;
+        }
 
+        *offset = ofs;
         if (*offset)
                 return 0;