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Subject[PATCH 15/37] perf trace: Introduce per-event maximum number of events property
Date
From: Arnaldo Carvalho de Melo <acme@redhat.com>

Call it 'nr', as in this context it should be expressive enough, i.e.:

# perf trace -e sched:*waking/nr=8,call-graph=fp/
0.000 :0/0 sched:sched_waking:comm=rcu_sched pid=10 prio=120 target_cpu=001
try_to_wake_up ([kernel.kallsyms])
sched_clock ([kernel.kallsyms])
3.933 :0/0 sched:sched_waking:comm=rcu_sched pid=10 prio=120 target_cpu=001
try_to_wake_up ([kernel.kallsyms])
sched_clock ([kernel.kallsyms])
3.970 IPDL Backgroun/3622 sched:sched_waking:comm=Gecko_IOThread pid=3569 prio=120 target_cpu=003
try_to_wake_up ([kernel.kallsyms])
__libc_write (/usr/lib64/libpthread-2.26.so)
20.069 IPDL Backgroun/3622 sched:sched_waking:comm=Gecko_IOThread pid=3569 prio=120 target_cpu=003
try_to_wake_up ([kernel.kallsyms])
__libc_write (/usr/lib64/libpthread-2.26.so)
37.170 IPDL Backgroun/3622 sched:sched_waking:comm=Gecko_IOThread pid=3569 prio=120 target_cpu=003
try_to_wake_up ([kernel.kallsyms])
__libc_write (/usr/lib64/libpthread-2.26.so)
53.267 IPDL Backgroun/3622 sched:sched_waking:comm=Gecko_IOThread pid=3569 prio=120 target_cpu=003
try_to_wake_up ([kernel.kallsyms])
__libc_write (/usr/lib64/libpthread-2.26.so)
70.365 IPDL Backgroun/3622 sched:sched_waking:comm=Gecko_IOThread pid=3569 prio=120 target_cpu=003
try_to_wake_up ([kernel.kallsyms])
__libc_write (/usr/lib64/libpthread-2.26.so)
75.781 Web Content/3649 sched:sched_waking:comm=JS Helper pid=3670 prio=120 target_cpu=000
try_to_wake_up ([kernel.kallsyms])
try_to_wake_up ([kernel.kallsyms])
wake_up_q ([kernel.kallsyms])
futex_wake ([kernel.kallsyms])
do_futex ([kernel.kallsyms])
__x64_sys_futex ([kernel.kallsyms])
do_syscall_64 ([kernel.kallsyms])
entry_SYSCALL_64_after_hwframe ([kernel.kallsyms])
pthread_cond_signal@@GLIBC_2.3.2 (/usr/lib64/libpthread-2.26.so)
#

# perf trace -e sched:*switch/nr=2/,block:*_plug/nr=4/,block:*_unplug/nr=1/,net:*dev_queue/nr=3,max-stack=16/
0.000 :0/0 sched:sched_switch:swapper/0:0 [120] S ==> trace:3367 [120]
0.046 :0/0 sched:sched_switch:swapper/1:0 [120] S ==> kworker/u16:58:2722 [120]
570.670 irq/50-iwlwifi/680 net:net_dev_queue:dev=wlp3s0 skbaddr=0xffff93498051ef00 len=66
__dev_queue_xmit ([kernel.kallsyms])
1106.141 jbd2/dm-0-8/476 block:block_plug:[jbd2/dm-0-8]
1106.175 jbd2/dm-0-8/476 block:block_unplug:[jbd2/dm-0-8] 1
1618.088 kworker/u16:30/2694 block:block_plug:[kworker/u16:30]
1810.000 :0/0 net:net_dev_queue:dev=vnet0 skbaddr=0xffff93498051ef00 len=52
__dev_queue_xmit ([kernel.kallsyms])
3857.974 :0/0 net:net_dev_queue:dev=vnet0 skbaddr=0xffff93498051f900 len=52
__dev_queue_xmit ([kernel.kallsyms])
4790.277 jbd2/dm-2-8/748 block:block_plug:[jbd2/dm-2-8]
4790.448 jbd2/dm-2-8/748 block:block_plug:[jbd2/dm-2-8]
#

The global --max-events has precendence:

# trace --max-events 3 -e sched:*switch/nr=2/,block:*_plug/nr=4/,block:*_unplug/nr=1/,net:*dev_queue/nr=3,max-stack=16/
0.000 :0/0 sched:sched_switch:swapper/0:0 [120] S ==> qemu-system-x86:2252 [120]
0.029 qemu-system-x8/2252 sched:sched_switch:qemu-system-x86:2252 [120] D ==> swapper/0:0 [120]
58.047 DNS Res~er #14/31661 net:net_dev_queue:dev=wlp3s0 skbaddr=0xffff9346966af100 len=84
__dev_queue_xmit ([kernel.kallsyms])
__libc_send (/usr/lib64/libpthread-2.26.so)
#

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-s4jswltvh660ughvg9nwngah@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/Documentation/perf-trace.txt | 20 ++++++++++++++++++++
tools/perf/builtin-trace.c | 19 +++++++++++++++++--
tools/perf/util/evsel.h | 1 +
3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-trace.txt b/tools/perf/Documentation/perf-trace.txt
index 0d1a1cd4d328..e113450503d2 100644
--- a/tools/perf/Documentation/perf-trace.txt
+++ b/tools/perf/Documentation/perf-trace.txt
@@ -285,6 +285,26 @@ Trace the next min page page fault to take place on the first CPU:
[0x18b26e6bc2bd] (/tmp/perf-17136.map)
#

+Trace the next two sched:sched_switch events, four block:*_plug events, the
+next block:*_unplug and the next three net:*dev_queue events, this last one
+with a backtrace of at most 16 entries, system wide:
+
+ # perf trace -e sched:*switch/nr=2/,block:*_plug/nr=4/,block:*_unplug/nr=1/,net:*dev_queue/nr=3,max-stack=16/
+ 0.000 :0/0 sched:sched_switch:swapper/2:0 [120] S ==> rcu_sched:10 [120]
+ 0.015 rcu_sched/10 sched:sched_switch:rcu_sched:10 [120] R ==> swapper/2:0 [120]
+ 254.198 irq/50-iwlwifi/680 net:net_dev_queue:dev=wlp3s0 skbaddr=0xffff93498051f600 len=66
+ __dev_queue_xmit ([kernel.kallsyms])
+ 273.977 :0/0 net:net_dev_queue:dev=wlp3s0 skbaddr=0xffff93498051f600 len=78
+ __dev_queue_xmit ([kernel.kallsyms])
+ 274.007 :0/0 net:net_dev_queue:dev=wlp3s0 skbaddr=0xffff93498051ff00 len=78
+ __dev_queue_xmit ([kernel.kallsyms])
+ 2930.140 kworker/u16:58/2722 block:block_plug:[kworker/u16:58]
+ 2930.162 kworker/u16:58/2722 block:block_unplug:[kworker/u16:58] 1
+ 4466.094 jbd2/dm-2-8/748 block:block_plug:[jbd2/dm-2-8]
+ 8050.123 kworker/u16:30/2694 block:block_plug:[kworker/u16:30]
+ 8050.271 kworker/u16:30/2694 block:block_plug:[kworker/u16:30]
+ #
+
SEE ALSO
--------
linkperf:perf-record[1], linkperf:perf-script[1]
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 589e0412652a..7081d7ea12e5 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2092,8 +2092,18 @@ static int trace__event_handler(struct trace *trace, struct perf_evsel *evsel,
union perf_event *event __maybe_unused,
struct perf_sample *sample)
{
- struct thread *thread = machine__findnew_thread(trace->host, sample->pid, sample->tid);
+ struct thread *thread;
int callchain_ret = 0;
+ /*
+ * Check if we called perf_evsel__disable(evsel) due to, for instance,
+ * this event's max_events having been hit and this is an entry coming
+ * from the ring buffer that we should discard, since the max events
+ * have already been considered/printed.
+ */
+ if (evsel->disabled)
+ return 0;
+
+ thread = machine__findnew_thread(trace->host, sample->pid, sample->tid);

if (sample->callchain) {
callchain_ret = trace__resolve_callchain(trace, evsel, sample, &callchain_cursor);
@@ -2142,6 +2152,11 @@ static int trace__event_handler(struct trace *trace, struct perf_evsel *evsel,
sample->raw_data, sample->raw_size,
trace->output);
++trace->nr_events_printed;
+
+ if (evsel->max_events != ULONG_MAX && ++evsel->nr_events_printed == evsel->max_events) {
+ perf_evsel__disable(evsel);
+ perf_evsel__close(evsel);
+ }
}
}

@@ -2726,7 +2741,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
int timeout = done ? 100 : -1;

if (!draining && perf_evlist__poll(evlist, timeout) > 0) {
- if (perf_evlist__filter_pollfd(evlist, POLLERR | POLLHUP) == 0)
+ if (perf_evlist__filter_pollfd(evlist, POLLERR | POLLHUP | POLLNVAL) == 0)
draining = true;

goto again;
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 4ef50f157b50..3147ca76c6fc 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -102,6 +102,7 @@ struct perf_evsel {
int idx;
u32 ids;
unsigned long max_events;
+ unsigned long nr_events_printed;
char *name;
double scale;
const char *unit;
--
2.14.4
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