[tip:perfcounters/core] perf top: Reduce display overhead

tip-bot for Mike Galbraith
2009-05-25T11:04:27Z

Commit-ID: d94b943054721c346b0881865d645f000cd19880
Gitweb: http://git.kernel.org/tip/d94b943054721c346b0881865d645f000cd19880
Author: Mike Galbraith <efault@gmx.de>
AuthorDate: Mon, 25 May 2009 09:57:56 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 25 May 2009 13:01:17 +0200

perf top: Reduce display overhead

Iterate over the symbol table once per display interval, and
copy/sort/tally/decay only those symbols which are active.

Before:

top - 10:14:53 up 4:08, 17 users, load average: 1.17, 1.53, 1.49
Tasks: 273 total, 5 running, 268 sleeping, 0 stopped, 0 zombie
Cpu(s): 6.9%us, 38.2%sy, 0.0%ni, 19.9%id, 0.0%wa, 0.0%hi, 35.0%si, 0.0%st

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND
28504 root 20 0 1044 260 164 S 58 0.0 0:04.19 2 netserver
28499 root 20 0 1040 412 316 R 51 0.0 0:04.15 0 netperf
28500 root 20 0 1040 408 316 R 50 0.0 0:04.14 1 netperf
28503 root 20 0 1044 260 164 S 50 0.0 0:04.01 1 netserver
28501 root 20 0 1044 260 164 S 49 0.0 0:03.99 0 netserver
28502 root 20 0 1040 412 316 S 43 0.0 0:03.96 2 netperf
28468 root 20 0 1892m 325m 972 S 16 10.8 0:10.50 3 perf
28467 root 20 0 1892m 325m 972 R 2 10.8 0:00.72 3 perf

After:

top - 10:16:30 up 4:10, 17 users, load average: 2.27, 1.88, 1.62
Tasks: 273 total, 6 running, 267 sleeping, 0 stopped, 0 zombie
Cpu(s): 2.5%us, 39.7%sy, 0.0%ni, 24.6%id, 0.0%wa, 0.0%hi, 33.3%si, 0.0%st

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND
28590 root 20 0 1040 412 316 S 54 0.0 0:07.85 2 netperf
28589 root 20 0 1044 260 164 R 54 0.0 0:07.84 0 netserver
28588 root 20 0 1040 412 316 R 50 0.0 0:07.89 1 netperf
28591 root 20 0 1044 256 164 S 50 0.0 0:07.82 1 netserver
28587 root 20 0 1040 408 316 R 47 0.0 0:07.61 0 netperf
28592 root 20 0 1044 260 164 R 47 0.0 0:07.85 2 netserver
28378 root 20 0 8732 1300 860 R 2 0.0 0:01.81 3 top
28577 root 20 0 1892m 165m 972 R 2 5.5 0:00.48 3 perf
28578 root 20 0 1892m 165m 972 S 2 5.5 0:00.04 3 perf

[ Impact: optimization ]

Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
Documentation/perf_counter/builtin-top.c | 56 +++++++++++++++--------------
1 files changed, 29 insertions(+), 27 deletions(-)

diff --git a/Documentation/perf_counter/builtin-top.c b/Documentation/perf_counter/builtin-top.c
index 74021ac..4bed265 100644
--- a/Documentation/perf_counter/builtin-top.c
+++ b/Documentation/perf_counter/builtin-top.c
@@ -374,18 +374,26 @@ static struct sym_entry tmp[MAX_SYMS];

static void print_sym_table(void)
{
- int i, printed;
+ int i, j, active_count, printed;
int counter;
float events_per_sec = events/delay_secs;
float kevents_per_sec = (events-userspace_events)/delay_secs;
float sum_kevents = 0.0;

events = userspace_events = 0;
- memcpy(tmp, sym_table, sizeof(sym_table[0])*sym_table_count);
- qsort(tmp, sym_table_count, sizeof(tmp[0]), compare);

- for (i = 0; i < sym_table_count && tmp[i].count[0]; i++)
- sum_kevents += tmp[i].count[0];
+ /* Iterate over symbol table and copy/tally/decay active symbols. */
+ for (i = 0, active_count = 0; i < sym_table_count; i++) {
+ if (sym_table[i].count[0]) {
+ tmp[active_count++] = sym_table[i];
+ sum_kevents += sym_table[i].count[0];
+
+ for (j = 0; j < nr_counters; j++)
+ sym_table[i].count[j] = zero ? 0 : sym_table[i].count[j] * 7 / 8;
+ }
+ }
+
+ qsort(tmp, active_count + 1, sizeof(tmp[0]), compare);

write(1, CONSOLE_CLEAR, strlen(CONSOLE_CLEAR));

@@ -433,29 +441,23 @@ static void print_sym_table(void)
" ______ ______ _____ ________________ _______________\n\n"
);

- for (i = 0, printed = 0; i < sym_table_count; i++) {
+ for (i = 0, printed = 0; i < active_count; i++) {
float pcnt;
- int count;

- if (printed <= 18 && tmp[i].count[0] >= count_filter) {
- pcnt = 100.0 - (100.0*((sum_kevents-tmp[i].count[0])/sum_kevents));
-
- if (nr_counters == 1)
- printf("%19.2f - %4.1f%% - %016llx : %s\n",
- sym_weight(tmp + i),
- pcnt, tmp[i].addr, tmp[i].sym);
- else
- printf("%8.1f %10ld - %4.1f%% - %016llx : %s\n",
- sym_weight(tmp + i),
- tmp[i].count[0],
- pcnt, tmp[i].addr, tmp[i].sym);
- printed++;
- }
- /*
- * Add decay to the counts:
- */
- for (count = 0; count < nr_counters; count++)
- sym_table[i].count[count] = zero ? 0 : sym_table[i].count[count] * 7 / 8;
+ if (++printed > 18 || tmp[i].count[0] < count_filter)
+ break;
+
+ pcnt = 100.0 - (100.0*((sum_kevents-tmp[i].count[0])/sum_kevents));
+
+ if (nr_counters == 1)
+ printf("%19.2f - %4.1f%% - %016llx : %s\n",
+ sym_weight(tmp + i),
+ pcnt, tmp[i].addr, tmp[i].sym);
+ else
+ printf("%8.1f %10ld - %4.1f%% - %016llx : %s\n",
+ sym_weight(tmp + i),
+ tmp[i].count[0],
+ pcnt, tmp[i].addr, tmp[i].sym);
}

if (sym_filter_entry)