perf.c

void PerfSampleWrap::signal_handler(int sig_num, siginfo_t *sig_info, void *context)
{
    perf_event_mmap_page *mmap_buffer = (perf_event_mmap_page *) data->buffers[index];
    while (__mmap_get_remain_size(mmap_buffer) > 0)
    {
        uint64_t remain = __mmap_get_remain_size(mmap_buffer);
        if (remain < sizeof(perf_event_header))
        {
            __mmap_move_index(mmap_buffer, remain);
            break;
        }
        PerfMySample *sample = (PerfMySample *) __mmap_get_index(mmap_buffer);
        if (sample->header.type == PERF_RECORD_SAMPLE)
        {
            __config.handler->callback(index, sample, context);
        }
        else
        {
            if (sample->header.size == 0)
            {
                __mmap_move_index(mmap_buffer, remain);
                break;
            }
        }
        __mmap_move_index(mmap_buffer, sample->header.size);
    }

}

void PerfSampleWrap::__mmap_move_index(perf_event_mmap_page *buffer, size_t n)
{
    assert(n <= __mmap_get_remain_size(buffer));
    buffer->data_tail += n;
}

void *PerfSampleWrap::__mmap_get_index(perf_event_mmap_page *buffer)
{
    char *data = (char *) buffer + PAGE_SIZE;
    uint64_t tail = buffer->data_tail & (PAGE_SIZE * RING_BUFFER_PAGES - 1);
    return data + tail;
}

uint64_t PerfSampleWrap::__mmap_get_remain_size(perf_event_mmap_page *buffer)
{
    uint64_t data_head = buffer->data_head;
    __sync_synchronize();
    return data_head - buffer->data_tail;
}