perf tools: Cache register accesses for unwind processing

Caching registers value into an array. Got about 4% speed up
of perf_reg_value function for report command processing
dwarf unwind stacks.

Output from report over 1.5 GB data with DWARF unwind stacks:
(TODO fix perf diff)

  current code:
   5.84%     perf  perf                       [.] perf_reg_value
  change:
   1.94%     perf  perf                       [.] perf_reg_value

And little bit of overall speed up:
(perf stat -r 5 -e '{cycles,instructions}:u' ...)

  current code:
   310,298,611,754      cycles                     ( +-  0.33% )
   439,669,689,341      instructions               ( +-  0.03% )

     188.656753166 seconds time elapsed            ( +-  0.82% )

  change:
   291,315,329,878      cycles                     ( +-  0.22% )
   391,763,485,304      instructions               ( +-  0.03%  )

     180.742249687 seconds time elapsed            ( +-  0.64% )

Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1401892622-30848-2-git-send-email-jolsa@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>

3 files changed, 17 insertions, 2 deletions

diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 9ba2eb3bdcfd..e5dd40addb30 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -7,6 +7,7 @@
 #include "../perf.h"
 #include "map.h"
 #include "build-id.h"
+#include "perf_regs.h"
 
 struct mmap_event {
         struct perf_event_header header;
@@ -89,6 +90,10 @@ struct regs_dump {
         u64 abi;
         u64 mask;
         u64 *regs;
+
+        /* Cached values/mask filled by first register access. */
+        u64 cache_regs[PERF_REGS_MAX];
+        u64 cache_mask;
 };
 
 struct stack_dump {
diff --git a/tools/perf/util/perf_regs.c b/tools/perf/util/perf_regs.c
index a3539ef30b15..43168fb0d9a2 100644
--- a/tools/perf/util/perf_regs.c
+++ b/tools/perf/util/perf_regs.c
@@ -1,11 +1,15 @@
 #include <errno.h>
 #include "perf_regs.h"
+#include "event.h"
 
 int perf_reg_value(u64 *valp, struct regs_dump *regs, int id)
 {
         int i, idx = 0;
         u64 mask = regs->mask;
 
+        if (regs->cache_mask & (1 << id))
+                goto out;
+
         if (!(mask & (1 << id)))
                 return -EINVAL;
 
@@ -14,6 +18,10 @@ int perf_reg_value(u64 *valp, struct regs_dump *regs, int id)
                         idx++;
         }
 
-        *valp = regs->regs[idx];
+        regs->cache_mask |= (1 << id);
+        regs->cache_regs[id] = regs->regs[idx];
+
+out:
+        *valp = regs->cache_regs[id];
         return 0;
 }
diff --git a/tools/perf/util/perf_regs.h b/tools/perf/util/perf_regs.h
index 79c78f74e0cf..980dbf76bc98 100644
--- a/tools/perf/util/perf_regs.h
+++ b/tools/perf/util/perf_regs.h
@@ -2,7 +2,8 @@
 #define __PERF_REGS_H
 
 #include <linux/types.h>
-#include "event.h"
+
+struct regs_dump;
 
 #ifdef HAVE_PERF_REGS_SUPPORT
 #include <perf_regs.h>
@@ -11,6 +12,7 @@ int perf_reg_value(u64 *valp, struct regs_dump *regs, int id);
 
 #else
 #define PERF_REGS_MASK  0
+#define PERF_REGS_MAX   0
 
 static inline const char *perf_reg_name(int id __maybe_unused)
 {