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Date: Thu, 24 Mar 2011 16:38:43 +0800
From: Lin Ming <ming.m.lin@...el.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: Arnaldo Carvalho de Melo <acme@...radead.org>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf probe: Add fastpath to do lookup by function name
On Thu, 2011-03-24 at 15:58 +0800, Ingo Molnar wrote:
> * Lin Ming <ming.m.lin@...el.com> wrote:
>
> > The vmlinux file may have thousands of CUs.
> > We can lookup function name from .debug_pubnames section
> > to avoid the slow loop on CUs.
>
> Mind including before/after perf stat --repeat 10 results in the changelog, of
> an affected command which got faster?
>From 611a823a34e655d47a80f92994b004391e2b244c Mon Sep 17 00:00:00 2001
From: Lin Ming <ming.m.lin@...el.com>
Date: Thu, 24 Mar 2011 23:22:24 +0800
Subject: [PATCH] perf probe: Add fastpath to do lookup by function name
The vmlinux file may have thousands of CUs.
We can lookup function name from .debug_pubnames section
to avoid the slow loop on CUs.
./perf stat -r 10 -- ./perf probe -k /home/mlin/vmlinux \
-s /home/mlin/linux-2.6 \
--line csum_partial_copy_to_user > tmp.log
before patch applied
=====================
364.535892 task-clock-msecs # 0.997 CPUs
0 context-switches # 0.000 M/sec
0 CPU-migrations # 0.000 M/sec
29,993 page-faults # 0.082 M/sec
865,862,109 cycles # 2375.245 M/sec
1,255,259,630 instructions # 1.450 IPC
252,400,884 branches # 692.390 M/sec
3,429,376 branch-misses # 1.359 %
1,386,990 cache-references # 3.805 M/sec
687,188 cache-misses # 1.885 M/sec
0.365792170 seconds time elapsed
after patch applied
=====================
89.896405 task-clock-msecs # 0.991 CPUs
1 context-switches # 0.000 M/sec
0 CPU-migrations # 0.000 M/sec
10,145 page-faults # 0.113 M/sec
214,553,875 cycles # 2386.679 M/sec
226,915,559 instructions # 1.058 IPC
44,536,614 branches # 495.422 M/sec
613,074 branch-misses # 1.377 %
860,787 cache-references # 9.575 M/sec
442,380 cache-misses # 4.921 M/sec
0.090716032 seconds time elapsed
Signed-off-by: Lin Ming <ming.m.lin@...el.com>
---
tools/perf/util/probe-finder.c | 38 ++++++++++++++++++++++++++++++++++++++
tools/perf/util/probe-finder.h | 1 +
2 files changed, 39 insertions(+), 0 deletions(-)
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 194f9e2..b2034c2 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1876,6 +1876,30 @@ static int find_line_range_by_func(struct line_finder *lf)
return param.retval;
}
+static int pubname_search_cb(Dwarf *dbg, Dwarf_Global *gl, void *data)
+{
+ struct line_finder *lf = data;
+ struct line_range *lr = lf->lr;
+
+ if (dwarf_offdie(dbg, gl->die_offset, &lf->sp_die)) {
+ if (dwarf_tag(&lf->sp_die) != DW_TAG_subprogram)
+ return DWARF_CB_OK;
+
+ if (die_compare_name(&lf->sp_die, lr->function)) {
+ if (!dwarf_offdie(dbg, gl->cu_offset, &lf->cu_die))
+ return DWARF_CB_OK;
+
+ if (lr->file && !cu_find_realpath(&lf->cu_die, lr->file))
+ return DWARF_CB_OK;
+
+ lf->found = 1;
+ return DWARF_CB_ABORT;
+ }
+ }
+
+ return DWARF_CB_OK;
+}
+
int find_line_range(int fd, struct line_range *lr)
{
struct line_finder lf = {.lr = lr, .found = 0};
@@ -1895,6 +1919,19 @@ int find_line_range(int fd, struct line_range *lr)
return -EBADF;
}
+ /* Fastpath: lookup by function name from .debug_pubnames section */
+ if (lr->function) {
+ struct dwarf_callback_param param = {.data = (void *)&lf, .retval = 0};
+
+ dwarf_getpubnames(dbg, pubname_search_cb, &lf, 0);
+ if (lf.found) {
+ lf.found = 0;
+ line_range_search_cb(&lf.sp_die, ¶m);
+ if (lf.found)
+ goto found;
+ }
+ }
+
/* Loop on CUs (Compilation Unit) */
while (!lf.found && ret >= 0) {
if (dwarf_nextcu(dbg, off, &noff, &cuhl, NULL, NULL, NULL) != 0)
@@ -1923,6 +1960,7 @@ int find_line_range(int fd, struct line_range *lr)
off = noff;
}
+found:
/* Store comp_dir */
if (lf.found) {
comp_dir = cu_get_comp_dir(&lf.cu_die);
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index beaefc3..4bc56a4 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -83,6 +83,7 @@ struct line_finder {
int lno_s; /* Start line number */
int lno_e; /* End line number */
Dwarf_Die cu_die; /* Current CU */
+ Dwarf_Die sp_die;
int found;
};
--
1.7.2.3
--
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