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

tip-bot for Ingo Molnar
2009-06-03T19:16:26Z

Commit-ID: eed4dcd443da7a46131ef37c7a389b444905960e
Gitweb: http://git.kernel.org/tip/eed4dcd443da7a46131ef37c7a389b444905960e
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Wed, 3 Jun 2009 19:59:24 +0200
Committer: Ingo Molnar <mingo@elte.hu>
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@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
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;
}