Method flush_to_disk

src/bthread/mutex.cpp:190–269

}

void ContentionProfiler::flush_to_disk(bool ending) {
    BT_VLOG << "flush_to_disk(ending=" << ending << ")";
    
    // Serialize contentions in _dedup_map into _disk_buf.
    if (!_dedup_map.empty()) {
        BT_VLOG << "dedup_map=" << _dedup_map.size();
        butil::IOBufBuilder os;
        for (ContentionMap::const_iterator
                 it = _dedup_map.begin(); it != _dedup_map.end(); ++it) {
            SampledContention* c = it->second;
            os << c->duration_ns << ' ' << (size_t)ceil(c->count) << " @";
            for (int i = SKIPPED_STACK_FRAMES; i < c->nframes; ++i) {
                os << ' ' << (void*)c->stack[i];
            }
            os << '\n';
            c->destroy();
        }
        _dedup_map.clear();
        _disk_buf.append(os.buf());
    }

    // Append /proc/self/maps to the end of the contention file, required by
    // pprof.pl, otherwise the functions in sys libs are not interpreted.
    if (ending) {
        BT_VLOG << "Append /proc/self/maps";
        // Failures are not critical, don't return directly.
        butil::IOPortal mem_maps;
        const butil::fd_guard fd(open("/proc/self/maps", O_RDONLY));
        if (fd >= 0) {
            while (true) {
                ssize_t nr = mem_maps.append_from_file_descriptor(fd, 8192);
                if (nr < 0) {
                    if (errno == EINTR) {
                        continue;
                    }
                    PLOG(ERROR) << "Fail to read /proc/self/maps";
                    break;
                }
                if (nr == 0) {
                    _disk_buf.append(mem_maps);
                    break;
                }
            }
        } else {
            PLOG(ERROR) << "Fail to open /proc/self/maps";
        }
    }
    // Write _disk_buf into _filename
    butil::File::Error error;
    butil::FilePath path(_filename);
    butil::FilePath dir = path.DirName();
    if (!butil::CreateDirectoryAndGetError(dir, &error)) {
        LOG(ERROR) << "Fail to create directory=`" << dir.value()
                   << "', " << error;
        return;
    }
    // Truncate on first write, append on later writes.
    int flag = O_APPEND;