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>

diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 3782c82c6e44b579895dc0b48f034f856706c8d4..ced92841ff97d75f2768fae0edba8e5971c93968 100644 (file)
--- 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 6edf535f65c23428b4982fb651ba3df997d55dfb..e3c40a520a253c73cbad3f4e04558f006508cdb7 100644 (file)
--- 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;