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liblog: benchmark add BM_log_event_overhead_42 for a well known tag

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Measure the cost of using a known test event log tag from
system/core/logcat/event.logtags:

42    answer (to life the universe etc|3)

Test: liblog_benchmarks BM_log_event_overhead_42
Bug: 36683634
Change-Id: Ibd4be82bebfcedd381c84e8078cf6d05a636aa98
This commit is contained in:
Mark Salyzyn 2017-03-28 11:40:55 -07:00
parent cf29755e28
commit fe8c96d152
2 changed files with 27 additions and 1 deletions
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26
liblog/tests/liblog_benchmark.cpp
View file

@ -527,11 +527,13 @@ BENCHMARK(BM_log_print_overhead);
/*
* Measure the time it takes to submit the android event logging call
* using discrete acquisition (StartBenchmarkTiming() -> StopBenchmarkTiming())
* under light load. Expect this to be a dozen or so syscall periods (40us)
* under light load. Expect this to be a long path to logger to convert the
* unknown tag (0) into a tagname (less than 200us).
*/
static void BM_log_event_overhead(int iters) {
for (unsigned long long i = 0; i < (unsigned)iters; ++i) {
StartBenchmarkTiming();
// log tag number 0 is not known, nor shall it ever be known
__android_log_btwrite(0, EVENT_TYPE_LONG, &i, sizeof(i));
StopBenchmarkTiming();
logd_yield();
@ -539,6 +541,28 @@ static void BM_log_event_overhead(int iters) {
}
BENCHMARK(BM_log_event_overhead);
/*
* Measure the time it takes to submit the android event logging call
* using discrete acquisition (StartBenchmarkTiming() -> StopBenchmarkTiming())
* under light load with a known logtag. Expect this to be a dozen or so
* syscall periods (less than 40us)
*/
static void BM_log_event_overhead_42(int iters) {
for (unsigned long long i = 0; i < (unsigned)iters; ++i) {
StartBenchmarkTiming();
// In system/core/logcat/event.logtags:
// # These are used for testing, do not modify without updating
// # tests/framework-tests/src/android/util/EventLogFunctionalTest.java.
// # system/core/liblog/tests/liblog_benchmark.cpp
// # system/core/liblog/tests/liblog_test.cpp
// 42 answer (to life the universe etc|3)
__android_log_btwrite(42, EVENT_TYPE_LONG, &i, sizeof(i));
StopBenchmarkTiming();
logd_yield();
}
}
BENCHMARK(BM_log_event_overhead_42);
static void BM_log_event_overhead_null(int iters) {
set_log_null();
BM_log_event_overhead(iters);

2
logcat/event.logtags
View file

@ -36,6 +36,8 @@
# These are used for testing, do not modify without updating
# tests/framework-tests/src/android/util/EventLogFunctionalTest.java.
# system/core/liblog/tests/liblog_benchmark.cpp
# system/core/liblog/tests/liblog_test.cpp
42 answer (to life the universe etc|3)
314 pi
2718 e