* [PATCH] perf stat: Poll for monitored tasks being alive in fork mode
@ 2019-01-04 2:28 Jin Yao
2019-01-04 12:54 ` Jiri Olsa
0 siblings, 1 reply; 6+ messages in thread
From: Jin Yao @ 2019-01-04 2:28 UTC (permalink / raw)
To: acme, jolsa, peterz, mingo, alexander.shishkin
Cc: Linux-kernel, ak, kan.liang, yao.jin, Jin Yao
Following test shows the stat keeps running even if no longer
task to monitor (mgen exits at ~5s).
perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
time counts unit events
1.000148916 1,308,365,864 cycles
2.000379171 1,297,269,875 cycles
3.000556719 1,297,187,078 cycles
4.000914241 761,261,827 cycles
5.001306091 <not counted> cycles
6.001676881 <not counted> cycles
7.002046336 <not counted> cycles
8.002405651 <not counted> cycles
9.002766625 <not counted> cycles
10.001395827 <not counted> cycles
We'd better finish stat immediately if there's no longer task to
monitor.
After:
perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
time counts unit events
1.000180062 1,236,592,661 cycles
2.000421539 1,223,733,572 cycles
3.000609910 1,297,047,663 cycles
4.000807545 1,297,215,816 cycles
5.001001578 1,297,208,032 cycles
6.001390345 582,343,659 cycles
sleep: Terminated
Now the stat exits immediately when the monitored tasks ends.
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
---
tools/perf/builtin-stat.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 63a3afc..71f3bc8 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -553,6 +553,13 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
if (interval || timeout) {
while (!waitpid(child_pid, &status, WNOHANG)) {
+ if (!is_target_alive(&target,
+ evsel_list->threads) &&
+ (child_pid != -1)) {
+ kill(child_pid, SIGTERM);
+ break;
+ }
+
nanosleep(&ts, NULL);
if (timeout)
break;
--
2.7.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] perf stat: Poll for monitored tasks being alive in fork mode
2019-01-04 2:28 [PATCH] perf stat: Poll for monitored tasks being alive in fork mode Jin Yao
@ 2019-01-04 12:54 ` Jiri Olsa
2019-01-05 3:16 ` Jin, Yao
0 siblings, 1 reply; 6+ messages in thread
From: Jiri Olsa @ 2019-01-04 12:54 UTC (permalink / raw)
To: Jin Yao
Cc: acme, jolsa, peterz, mingo, alexander.shishkin, Linux-kernel, ak,
kan.liang, yao.jin
On Fri, Jan 04, 2019 at 10:28:17AM +0800, Jin Yao wrote:
> Following test shows the stat keeps running even if no longer
> task to monitor (mgen exits at ~5s).
>
> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
> time counts unit events
> 1.000148916 1,308,365,864 cycles
> 2.000379171 1,297,269,875 cycles
> 3.000556719 1,297,187,078 cycles
> 4.000914241 761,261,827 cycles
> 5.001306091 <not counted> cycles
> 6.001676881 <not counted> cycles
> 7.002046336 <not counted> cycles
> 8.002405651 <not counted> cycles
> 9.002766625 <not counted> cycles
> 10.001395827 <not counted> cycles
>
> We'd better finish stat immediately if there's no longer task to
> monitor.
>
> After:
>
> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
> time counts unit events
> 1.000180062 1,236,592,661 cycles
> 2.000421539 1,223,733,572 cycles
> 3.000609910 1,297,047,663 cycles
> 4.000807545 1,297,215,816 cycles
> 5.001001578 1,297,208,032 cycles
> 6.001390345 582,343,659 cycles
> sleep: Terminated
>
> Now the stat exits immediately when the monitored tasks ends.
>
> Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
> ---
> tools/perf/builtin-stat.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 63a3afc..71f3bc8 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -553,6 +553,13 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>
> if (interval || timeout) {
> while (!waitpid(child_pid, &status, WNOHANG)) {
> + if (!is_target_alive(&target,
> + evsel_list->threads) &&
> + (child_pid != -1)) {
do we need that child_pid check? we just returned from waitpid
so we should be ok.. we just make the race window smaller
could we just do:
if (!is_target_alive(&target, evsel_list->threads)) {
kill(child_pid, SIGTERM);
break;
}
also I'm not sure we should do this only under new option,
as it might break people's scripts.. thoughts?
jirka
> + kill(child_pid, SIGTERM);
> + break;
> + }
> +
> nanosleep(&ts, NULL);
> if (timeout)
> break;
> --
> 2.7.4
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] perf stat: Poll for monitored tasks being alive in fork mode
2019-01-04 12:54 ` Jiri Olsa
@ 2019-01-05 3:16 ` Jin, Yao
2019-01-06 13:25 ` Jiri Olsa
0 siblings, 1 reply; 6+ messages in thread
From: Jin, Yao @ 2019-01-05 3:16 UTC (permalink / raw)
To: Jiri Olsa
Cc: acme, jolsa, peterz, mingo, alexander.shishkin, Linux-kernel, ak,
kan.liang, yao.jin
On 1/4/2019 8:54 PM, Jiri Olsa wrote:
> On Fri, Jan 04, 2019 at 10:28:17AM +0800, Jin Yao wrote:
>> Following test shows the stat keeps running even if no longer
>> task to monitor (mgen exits at ~5s).
>>
>> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
>> time counts unit events
>> 1.000148916 1,308,365,864 cycles
>> 2.000379171 1,297,269,875 cycles
>> 3.000556719 1,297,187,078 cycles
>> 4.000914241 761,261,827 cycles
>> 5.001306091 <not counted> cycles
>> 6.001676881 <not counted> cycles
>> 7.002046336 <not counted> cycles
>> 8.002405651 <not counted> cycles
>> 9.002766625 <not counted> cycles
>> 10.001395827 <not counted> cycles
>>
>> We'd better finish stat immediately if there's no longer task to
>> monitor.
>>
>> After:
>>
>> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
>> time counts unit events
>> 1.000180062 1,236,592,661 cycles
>> 2.000421539 1,223,733,572 cycles
>> 3.000609910 1,297,047,663 cycles
>> 4.000807545 1,297,215,816 cycles
>> 5.001001578 1,297,208,032 cycles
>> 6.001390345 582,343,659 cycles
>> sleep: Terminated
>>
>> Now the stat exits immediately when the monitored tasks ends.
>>
>> Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
>> ---
>> tools/perf/builtin-stat.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>> index 63a3afc..71f3bc8 100644
>> --- a/tools/perf/builtin-stat.c
>> +++ b/tools/perf/builtin-stat.c
>> @@ -553,6 +553,13 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>>
>> if (interval || timeout) {
>> while (!waitpid(child_pid, &status, WNOHANG)) {
>> + if (!is_target_alive(&target,
>> + evsel_list->threads) &&
>> + (child_pid != -1)) {
>
> do we need that child_pid check? we just returned from waitpid
> so we should be ok.. we just make the race window smaller
>
> could we just do:
>
> if (!is_target_alive(&target, evsel_list->threads)) {
> kill(child_pid, SIGTERM);
> break;
> }
>
I think this code should be OK and I have tested yet. I have a question
about the race condition, we really don't need a lock to protect the
child_pid?
skip_signal()
{
/*
* render child_pid harmless
* won't send SIGTERM to a random
* process in case of race condition
* and fast PID recycling
*/
child_pid = -1;
}
__run_perf_stat()
{
....
kill(child_pid, SIGTERM);
}
If child_pid is set by -1 in a small window between checking of
child_pid and kill(), then kill(-1, SIGTERM) may happen. All processes
except the kill process itself and init would receive SIGTERM.
Is this case possible?
> also I'm not sure we should do this only under new option,
> as it might break people's scripts.. thoughts?
>
> jirka
>
In current behavior, for non fork mode, if we terminate the monitored
task, the perf stat would return immediately. So I think this patch
should be OK.
Thanks
Jin Yao
>> + kill(child_pid, SIGTERM);
>> + break;
>> + }
>> +
>> nanosleep(&ts, NULL);
>> if (timeout)
>> break;
>> --
>> 2.7.4
>>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] perf stat: Poll for monitored tasks being alive in fork mode
2019-01-05 3:16 ` Jin, Yao
@ 2019-01-06 13:25 ` Jiri Olsa
2019-01-06 14:02 ` Jin, Yao
0 siblings, 1 reply; 6+ messages in thread
From: Jiri Olsa @ 2019-01-06 13:25 UTC (permalink / raw)
To: Jin, Yao
Cc: acme, jolsa, peterz, mingo, alexander.shishkin, Linux-kernel, ak,
kan.liang, yao.jin
On Sat, Jan 05, 2019 at 11:16:40AM +0800, Jin, Yao wrote:
>
>
> On 1/4/2019 8:54 PM, Jiri Olsa wrote:
> > On Fri, Jan 04, 2019 at 10:28:17AM +0800, Jin Yao wrote:
> > > Following test shows the stat keeps running even if no longer
> > > task to monitor (mgen exits at ~5s).
> > >
> > > perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
> > > time counts unit events
> > > 1.000148916 1,308,365,864 cycles
> > > 2.000379171 1,297,269,875 cycles
> > > 3.000556719 1,297,187,078 cycles
> > > 4.000914241 761,261,827 cycles
> > > 5.001306091 <not counted> cycles
> > > 6.001676881 <not counted> cycles
> > > 7.002046336 <not counted> cycles
> > > 8.002405651 <not counted> cycles
> > > 9.002766625 <not counted> cycles
> > > 10.001395827 <not counted> cycles
> > >
> > > We'd better finish stat immediately if there's no longer task to
> > > monitor.
> > >
> > > After:
> > >
> > > perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
> > > time counts unit events
> > > 1.000180062 1,236,592,661 cycles
> > > 2.000421539 1,223,733,572 cycles
> > > 3.000609910 1,297,047,663 cycles
> > > 4.000807545 1,297,215,816 cycles
> > > 5.001001578 1,297,208,032 cycles
> > > 6.001390345 582,343,659 cycles
> > > sleep: Terminated
> > >
> > > Now the stat exits immediately when the monitored tasks ends.
> > >
> > > Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
> > > ---
> > > tools/perf/builtin-stat.c | 7 +++++++
> > > 1 file changed, 7 insertions(+)
> > >
> > > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > > index 63a3afc..71f3bc8 100644
> > > --- a/tools/perf/builtin-stat.c
> > > +++ b/tools/perf/builtin-stat.c
> > > @@ -553,6 +553,13 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
> > > if (interval || timeout) {
> > > while (!waitpid(child_pid, &status, WNOHANG)) {
> > > + if (!is_target_alive(&target,
> > > + evsel_list->threads) &&
> > > + (child_pid != -1)) {
> >
> > do we need that child_pid check? we just returned from waitpid
> > so we should be ok.. we just make the race window smaller
> >
> > could we just do:
> >
> > if (!is_target_alive(&target, evsel_list->threads)) {
> > kill(child_pid, SIGTERM);
> > break;
> > }
> >
>
> I think this code should be OK and I have tested yet. I have a question
> about the race condition, we really don't need a lock to protect the
> child_pid?
>
> skip_signal()
> {
> /*
> * render child_pid harmless
> * won't send SIGTERM to a random
> * process in case of race condition
> * and fast PID recycling
> */
> child_pid = -1;
> }
>
> __run_perf_stat()
> {
> ....
> kill(child_pid, SIGTERM);
> }
>
> If child_pid is set by -1 in a small window between checking of child_pid
> and kill(), then kill(-1, SIGTERM) may happen. All processes except the kill
> process itself and init would receive SIGTERM.
ah right, -1 is special.. however that can still happen also
in the orginal patch.. how about we do something like below
jirka
---
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index acfd48db52dd..c322cb271180 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -583,6 +583,14 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
if (interval || timeout) {
while (!waitpid(child_pid, &status, WNOHANG)) {
+ if (!is_target_alive(&target, evsel_list->threads)) {
+ int pid = child_pid;
+
+ if (pid != -1)
+ kill(pid, SIGTERM);
+ break;
+ }
+
nanosleep(&ts, NULL);
if (timeout)
break;
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] perf stat: Poll for monitored tasks being alive in fork mode
2019-01-06 13:25 ` Jiri Olsa
@ 2019-01-06 14:02 ` Jin, Yao
2019-01-06 15:57 ` Jiri Olsa
0 siblings, 1 reply; 6+ messages in thread
From: Jin, Yao @ 2019-01-06 14:02 UTC (permalink / raw)
To: Jiri Olsa
Cc: acme, jolsa, peterz, mingo, alexander.shishkin, Linux-kernel, ak,
kan.liang, yao.jin
On 1/6/2019 9:25 PM, Jiri Olsa wrote:
> On Sat, Jan 05, 2019 at 11:16:40AM +0800, Jin, Yao wrote:
>>
>>
>> On 1/4/2019 8:54 PM, Jiri Olsa wrote:
>>> On Fri, Jan 04, 2019 at 10:28:17AM +0800, Jin Yao wrote:
>>>> Following test shows the stat keeps running even if no longer
>>>> task to monitor (mgen exits at ~5s).
>>>>
>>>> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
>>>> time counts unit events
>>>> 1.000148916 1,308,365,864 cycles
>>>> 2.000379171 1,297,269,875 cycles
>>>> 3.000556719 1,297,187,078 cycles
>>>> 4.000914241 761,261,827 cycles
>>>> 5.001306091 <not counted> cycles
>>>> 6.001676881 <not counted> cycles
>>>> 7.002046336 <not counted> cycles
>>>> 8.002405651 <not counted> cycles
>>>> 9.002766625 <not counted> cycles
>>>> 10.001395827 <not counted> cycles
>>>>
>>>> We'd better finish stat immediately if there's no longer task to
>>>> monitor.
>>>>
>>>> After:
>>>>
>>>> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
>>>> time counts unit events
>>>> 1.000180062 1,236,592,661 cycles
>>>> 2.000421539 1,223,733,572 cycles
>>>> 3.000609910 1,297,047,663 cycles
>>>> 4.000807545 1,297,215,816 cycles
>>>> 5.001001578 1,297,208,032 cycles
>>>> 6.001390345 582,343,659 cycles
>>>> sleep: Terminated
>>>>
>>>> Now the stat exits immediately when the monitored tasks ends.
>>>>
>>>> Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
>>>> ---
>>>> tools/perf/builtin-stat.c | 7 +++++++
>>>> 1 file changed, 7 insertions(+)
>>>>
>>>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>>>> index 63a3afc..71f3bc8 100644
>>>> --- a/tools/perf/builtin-stat.c
>>>> +++ b/tools/perf/builtin-stat.c
>>>> @@ -553,6 +553,13 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>>>> if (interval || timeout) {
>>>> while (!waitpid(child_pid, &status, WNOHANG)) {
>>>> + if (!is_target_alive(&target,
>>>> + evsel_list->threads) &&
>>>> + (child_pid != -1)) {
>>>
>>> do we need that child_pid check? we just returned from waitpid
>>> so we should be ok.. we just make the race window smaller
>>>
>>> could we just do:
>>>
>>> if (!is_target_alive(&target, evsel_list->threads)) {
>>> kill(child_pid, SIGTERM);
>>> break;
>>> }
>>>
>>
>> I think this code should be OK and I have tested yet. I have a question
>> about the race condition, we really don't need a lock to protect the
>> child_pid?
>>
>> skip_signal()
>> {
>> /*
>> * render child_pid harmless
>> * won't send SIGTERM to a random
>> * process in case of race condition
>> * and fast PID recycling
>> */
>> child_pid = -1;
>> }
>>
>> __run_perf_stat()
>> {
>> ....
>> kill(child_pid, SIGTERM);
>> }
>>
>> If child_pid is set by -1 in a small window between checking of child_pid
>> and kill(), then kill(-1, SIGTERM) may happen. All processes except the kill
>> process itself and init would receive SIGTERM.
>
> ah right, -1 is special.. however that can still happen also
> in the orginal patch.. how about we do something like below
>
> jirka
>
>
> ---
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index acfd48db52dd..c322cb271180 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -583,6 +583,14 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>
> if (interval || timeout) {
> while (!waitpid(child_pid, &status, WNOHANG)) {
> + if (!is_target_alive(&target, evsel_list->threads)) {
> + int pid = child_pid;
> +
> + if (pid != -1)
> + kill(pid, SIGTERM);
> + break;
> + }
> +
> nanosleep(&ts, NULL);
> if (timeout)
> break;
>
Hi Jiri,
I think your patch is good. At least, we can avoid the case of kill(-1,
SIGTERM).
BTW, you post this patch or I re-post it, both fine for me. :)
Thanks
Jin Yao
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] perf stat: Poll for monitored tasks being alive in fork mode
2019-01-06 14:02 ` Jin, Yao
@ 2019-01-06 15:57 ` Jiri Olsa
0 siblings, 0 replies; 6+ messages in thread
From: Jiri Olsa @ 2019-01-06 15:57 UTC (permalink / raw)
To: Jin, Yao
Cc: acme, jolsa, peterz, mingo, alexander.shishkin, Linux-kernel, ak,
kan.liang, yao.jin
On Sun, Jan 06, 2019 at 10:02:18PM +0800, Jin, Yao wrote:
SNIP
> > ---
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index acfd48db52dd..c322cb271180 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -583,6 +583,14 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
> > if (interval || timeout) {
> > while (!waitpid(child_pid, &status, WNOHANG)) {
> > + if (!is_target_alive(&target, evsel_list->threads)) {
> > + int pid = child_pid;
> > +
> > + if (pid != -1)
> > + kill(pid, SIGTERM);
> > + break;
> > + }
> > +
> > nanosleep(&ts, NULL);
> > if (timeout)
> > break;
> >
>
> Hi Jiri,
>
> I think your patch is good. At least, we can avoid the case of kill(-1,
> SIGTERM).
>
> BTW, you post this patch or I re-post it, both fine for me. :)
please post it
thanks,
jirka
^ permalink raw reply [flat|nested] 6+ messages in thread
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2019-01-04 2:28 [PATCH] perf stat: Poll for monitored tasks being alive in fork mode Jin Yao
2019-01-04 12:54 ` Jiri Olsa
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2019-01-06 13:25 ` Jiri Olsa
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