[tip:perfcounters/core] perf report: Add front-entry cache for lookups

[tip-bot for Ingo Molnar]

Commit-ID:  eed4dcd443da7a46131ef37c7a389b444905960e
Gitweb:     http://git.kernel.org/tip/eed4dcd443da7a46131ef37c7a389b444905960e
Author:     Ingo Molnar <mingo@xxxxxxx>
AuthorDate: Wed, 3 Jun 2009 19:59:24 +0200
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 3 Jun 2009 20:03:32 +0200

perf report: Add front-entry cache for lookups

Before:

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

     12453988058  instructions

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

     12379566017  instructions

0.60% reduction.

Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 Documentation/perf_counter/builtin-report.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/Documentation/perf_counter/builtin-report.c b/Documentation/perf_counter/builtin-report.c
index e837bb9..33b3b15 100644
--- a/Documentation/perf_counter/builtin-report.c
+++ b/Documentation/perf_counter/builtin-report.c
@@ -229,6 +229,7 @@ static int thread__set_comm(struct thread *self, const char *comm)
 }
 
 static struct rb_root threads;
+static struct thread *last_match;
 
 static struct thread *threads__findnew(pid_t pid)
 {
@@ -236,12 +237,22 @@ static struct thread *threads__findnew(pid_t pid)
 	struct rb_node *parent = NULL;
 	struct thread *th;
 
+	/*
+	 * Font-end cache - PID lookups come in blocks,
+	 * so most of the time we dont have to look up
+	 * the full rbtree:
+	 */
+	if (last_match && last_match->pid == pid)
+		return last_match;
+
 	while (*p != NULL) {
 		parent = *p;
 		th = rb_entry(parent, struct thread, rb_node);
 
-		if (th->pid == pid)
+		if (th->pid == pid) {
+			last_match = th;
 			return th;
+		}
 
 		if (pid < th->pid)
 			p = &(*p)->rb_left;
@@ -253,7 +264,9 @@ static struct thread *threads__findnew(pid_t pid)
 	if (th != NULL) {
 		rb_link_node(&th->rb_node, parent, p);
 		rb_insert_color(&th->rb_node, &threads);
+		last_match = th;
 	}
+
 	return th;
 }
 
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