From: Kan Liang <kan.li...@intel.com>
The interval-print used to be limited to 100ms. However, for example,
10ms is required to do sophisticated bandwidth analysis using uncore
event.
The test shows that the overhead of the system-wide uncore monitoring
with 10ms interval is only ~2%. So this patch reduces interval-print to
10ms.
But 10ms may not work well for all cases. For example, when the
cpus/threads number is very large, for system-wide core event monitoring
the overhead could be high. To handle this issue, a warning will be
displayed when the interval-print is set between 10ms to 100ms. So the
users can make a decision according to their specific cases.
#perf stat -e uncore_imc_1/cas_count_read/ -a --interval-print 10 --
sleep 1
print interval < 100ms. The overhead percentage could be high in some
cases. Please proceed with caution.
# time counts unit events
0.010200451 0.10 MiB uncore_imc_1/cas_count_read/
0.020475117 0.02 MiB uncore_imc_1/cas_count_read/
0.030692800 0.01 MiB uncore_imc_1/cas_count_read/
0.040948161 0.02 MiB uncore_imc_1/cas_count_read/
0.051159564 0.00 MiB uncore_imc_1/cas_count_read/
Signed-off-by: Kan Liang <kan.li...@intel.com>
---
tools/perf/Documentation/perf-stat.txt | 2 +-
tools/perf/builtin-stat.c | 13 +++++++++----
2 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/tools/perf/Documentation/perf-stat.txt
b/tools/perf/Documentation/perf-stat.txt
index 47469ab..7586fe0 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -128,7 +128,7 @@ perf stat --repeat 10 --null --sync --pre 'make -s
O=defconfig-build/clean' -- m
-I msecs::
--interval-print msecs::
- Print count deltas every N milliseconds (minimum: 100ms)
+ Print count deltas every N milliseconds (minimum: 10ms)
example: perf stat -I 1000 -e cycles -a sleep 5
--per-socket::
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index a96fb5c..5ef88f7 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -1179,7 +1179,7 @@ int cmd_stat(int argc, const char **argv, const char
*prefix __maybe_unused)
OPT_STRING(0, "post", &post_cmd, "command",
"command to run after to the measured command"),
OPT_UINTEGER('I', "interval-print", &stat_config.interval,
- "print counts at regular interval in ms (>= 100)"),
+ "print counts at regular interval in ms (>= 10)"),
OPT_SET_UINT(0, "per-socket", &stat_config.aggr_mode,
"aggregate counts per processor socket", AGGR_SOCKET),
OPT_SET_UINT(0, "per-core", &stat_config.aggr_mode,
@@ -1332,9 +1332,14 @@ int cmd_stat(int argc, const char **argv, const char
*prefix __maybe_unused)
thread_map__read_comms(evsel_list->threads);
if (interval && interval < 100) {
- pr_err("print interval must be >= 100ms\n");
- parse_options_usage(stat_usage, options, "I", 1);
- goto out;
+ if (interval < 10) {
+ pr_err("print interval must be >= 10ms\n");
+ parse_options_usage(stat_usage, options, "I", 1);
+ goto out;
+ } else
+ pr_warning("print interval < 100ms. "
+ "The overhead percentage could be high in
some cases. "
+ "Please proceed with caution.\n");
}
if (perf_evlist__alloc_stats(evsel_list, interval))
--
1.8.3.1
--
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