[PATCH 1/3] perf tools: Cache register accesses for unwind processing

[Jiri Olsa]

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:
   6.81%  perf.old  perf.old                   [.] perf_reg_value

  change:
   2.24%  perf      perf                       [.] perf_reg_value

And little bit of speed up:

 Performance counter stats for './perf.old report -i perf-test.data --stdio':

   134,664,011,577      cycles:u                  #    2.472 GHz
   189,677,227,475      instructions:u            #    1.41  insns per cycle
      54465.096050      task-clock (msec)         #    0.998 CPUs utilized

      54.598339009 seconds time elapsed

 Performance counter stats for './perf report -i perf-test.data --stdio':

   124,478,681,672      cycles:u                  #    2.466 GHz
   168,998,379,866      instructions:u            #    1.36  insns per cycle
      50487.110482      task-clock (msec)         #    0.997 CPUs utilized

      50.635824229 seconds time elapsed

Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: Jean Pihet <jean.pihet@xxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 tools/perf/util/event.h     |  5 +++++
 tools/perf/util/perf_regs.c | 10 +++++++++-
 tools/perf/util/perf_regs.h |  4 +++-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 38457d4..970d4eb 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;
@@ -87,6 +88,10 @@ 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 a3539ef..43168fb 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 d6e8b6a..80d8ab1 100644
--- a/tools/perf/util/perf_regs.h
+++ b/tools/perf/util/perf_regs.h
@@ -2,15 +2,17 @@
 #define __PERF_REGS_H
 
 #include "types.h"
-#include "event.h"
 
 #ifdef HAVE_PERF_REGS_SUPPORT
 #include <perf_regs.h>
 
+struct regs_dump;
+
 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)
 {
-- 
1.8.3.1

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