perf tools powerpc: Cache the DWARF debug info

Cache the DWARF debug info for DSO so we don't have to rebuild it for each
address in the DSO.

Note that dso__new() uses calloc() so don't need to set dso->dwfl to NULL.

	$ /tmp/perf.orig --version
	perf version 3.18.rc1.gc2661b8
	$ /tmp/perf.new --version
	perf version 3.18.rc1.g402d62
	$ perf stat -e cycles,instructions /tmp/perf.orig report -g > orig

	 Performance counter stats for '/tmp/perf.orig report -g':

	     6,428,177,183 cycles                    #    0.000 GHz
	     4,176,288,391 instructions              #    0.65  insns per cycle

	       1.840666132 seconds time elapsed

	$ perf stat -e cycles,instructions /tmp/perf.new report -g > new

	 Performance counter stats for '/tmp/perf.new report -g':

	       305,773,142 cycles                    #    0.000 GHz
	       276,048,272 instructions              #    0.90  insns per cycle

	       0.087693543 seconds time elapsed
	$ diff orig new
	$

Changelog[v2]:

[Arnaldo Carvalho] Cache in existing global objects rather than create
                   new static/globals in functions.

Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Anton Blanchard <anton@au1.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20141022000958.GB2228@us.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 23 insertions, 11 deletions

diff --git a/tools/perf/arch/powerpc/util/skip-callchain-idx.c b/tools/perf/arch/powerpc/util/skip-callchain-idx.c
index d73ef8bb08c7..9892b0f0bec4 100644
--- a/tools/perf/arch/powerpc/util/skip-callchain-idx.c
+++ b/tools/perf/arch/powerpc/util/skip-callchain-idx.c
@@ -145,7 +145,7 @@ static Dwarf_Frame *get_dwarf_frame(Dwfl_Module *mod, Dwarf_Addr pc)
  *              yet used)
  *      -1 in case of errors
  */
-static int check_return_addr(const char *exec_file, Dwarf_Addr pc)
+static int check_return_addr(struct dso *dso, Dwarf_Addr pc)
 {
         int             rc = -1;
         Dwfl            *dwfl;
@@ -156,15 +156,27 @@ static int check_return_addr(const char *exec_file, Dwarf_Addr pc)
         Dwarf_Addr      end = pc;
         bool            signalp;
 
-        dwfl = dwfl_begin(&offline_callbacks);
-        if (!dwfl) {
-                pr_debug("dwfl_begin() failed: %s\n", dwarf_errmsg(-1));
-                return -1;
-        }
+        dwfl = dso->dwfl;
 
-        if (dwfl_report_offline(dwfl, "",  exec_file, -1) == NULL) {
-                pr_debug("dwfl_report_offline() failed %s\n", dwarf_errmsg(-1));
-                goto out;
+        if (!dwfl) {
+                dwfl = dwfl_begin(&offline_callbacks);
+                if (!dwfl) {
+                        pr_debug("dwfl_begin() failed: %s\n", dwarf_errmsg(-1));
+                        return -1;
+                }
+
+                if (dwfl_report_offline(dwfl, "", dso->long_name, -1) == NULL) {
+                        pr_debug("dwfl_report_offline() failed %s\n",
+                                                dwarf_errmsg(-1));
+                        /*
+                         * We normally cache the DWARF debug info and never
+                         * call dwfl_end(). But to prevent fd leak, free in
+                         * case of error.
+                         */
+                        dwfl_end(dwfl);
+                        goto out;
+                }
+                dso->dwfl = dwfl;
         }
 
         mod = dwfl_addrmodule(dwfl, pc);
@@ -194,7 +206,6 @@ static int check_return_addr(const char *exec_file, Dwarf_Addr pc)
         rc = check_return_reg(ra_regno, frame);
 
 out:
-        dwfl_end(dwfl);
         return rc;
 }
 
@@ -246,7 +257,7 @@ int arch_skip_callchain_idx(struct machine *machine, struct thread *thread,
                 return skip_slot;
         }
 
-        rc = check_return_addr(dso->long_name, ip);
+        rc = check_return_addr(dso, ip);
 
         pr_debug("DSO %s, nr %" PRIx64 ", ip 0x%" PRIx64 "rc %d\n",
                                 dso->long_name, chain->nr, ip, rc);
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index acb651acc7fd..3c9b391493f9 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -127,6 +127,7 @@ struct dso {
         const char       *long_name;
         u16              long_name_len;
         u16              short_name_len;
+        void            *dwfl;                  /* DWARF debug info */
 
         /* dso data file */
         struct {