gitccl commented on issue #2640:
URL: https://github.com/apache/brpc/issues/2640#issuecomment-2980336773
I agree that accurately computing `bthread_worker_usage` within the bthread
framework is quite challenging, especially since some tasks may run for
extended periods without yielding. Rather than striving for exact precision, we
could use a bounded estimation to ensure that `bthread_worker_usage` not
exceeds `bthread_worker_count`.
Here’s a possible solution:
* For each `TaskGroup`, add:
* `_cur_cumulated_worker_time_ns`: stores the cumulative worker time as
observed by bvar.
* `_last_cumulated_cputime_ns`: stores the value of
`TaskGroup::_cumulated_cputime_ns` at the time of the last observation.
* For `TaskControl`, add:
* `_last_observation_time`: records the timestamp of the last observation.
Updated `get_cumulated_worker_time()` Implementation：
```cpp
double TaskControl::get_cumulated_worker_time() {
int64_t cputime_ns = 0;
BAIDU_SCOPED_LOCK(_modify_group_mutex);
int64_t now = butil::cpuwide_time_ns();
for_each_task_group([&](TaskGroup* g) {
if (g) {
int64_t cur_cumulated_cputime_ns = g->_cumulated_cputime_ns;
g->_cur_cumulated_worker_time_ns += std::min(now -
_last_observation_time,
cur_cumulated_cputime_ns - g->_last_cumulated_cputime_ns);
g->_last_cumulated_cputime_ns = cur_cumulated_cputime_ns;
cputime_ns += g->_cur_cumulated_worker_time_ns;
}
});
_last_observation_time = now;
return cputime_ns / 1000000000.0;
}
```
This approach ensures that the reported `bthread_worker_usage` stays within
a reasonable and bounded range by constraining its growth based on both elapsed
wall clock time and actual CPU time consumed. It should effectively prevent the
metric from exceeding `bthread_worker_count`, even in cases of long-running,
non-yielding tasks.
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