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Clearer error message for perf mmap failure

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This commit is contained in:
Charlie Curtsinger 2019-10-08 09:56:51 -05:00
parent e71b89b024
commit 52505ca380
1 changed files with 3 additions and 1 deletions
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libcoz/perf.cpp
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@ -76,7 +76,9 @@ perf_event::perf_event(struct perf_event_attr& pe, pid_t pid, int cpu) :
// If sampling, map the perf event file
if(pe.sample_type != 0 && pe.sample_period != 0) {
void* ring_buffer = mmap(NULL, MmapSize, PROT_READ | PROT_WRITE, MAP_SHARED, _fd, 0);
REQUIRE(ring_buffer != MAP_FAILED) << "Failed to mmap perf event file";
REQUIRE(ring_buffer != MAP_FAILED) << "Mapping perf_event ring buffer failed. "
<< "Make sure the current user has permission to invoke the perf tool, and that "
<< "the program being profiled does not use an excessive number of threads (>1000).\n";
_mapping = reinterpret_cast<struct perf_event_mmap_page*>(ring_buffer);
}