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SubjectRe: [PATCH v2 2/2]: perf record: enable asynchronous trace writing
On Thu, Aug 23, 2018 at 07:47:01PM +0300, Alexey Budankov wrote:

SNIP

>
> static volatile int done;
> @@ -528,13 +530,85 @@ static struct perf_event_header finished_round_event = {
> .type = PERF_RECORD_FINISHED_ROUND,
> };
>
> +static int record__mmap_read_sync(int trace_fd, struct aiocb **cblocks,
> + int cblocks_size, struct record *rec)
> +{
> + size_t rem;
> + ssize_t size;
> + off_t rem_off;
> + int i, aio_ret, aio_errno, do_suspend;
> + struct perf_mmap *md;
> + struct timespec timeout0 = { 0, 0 };
> + struct timespec timeoutS = { 0, 1000 * 1000 * 1 };
> +
> + if (!cblocks_size)
> + return 0;
> +
> + do {
> + do_suspend = 0;
> + nanosleep(&timeoutS, NULL);
> + if (aio_suspend((const struct aiocb**)cblocks, cblocks_size, &timeout0)) {
> + if (errno == EAGAIN || errno == EINTR) {
> + do_suspend = 1;
> + continue;
> + } else {
> + pr_err("failed to sync perf data, error: %m\n");
> + break;
> + }
> + }
> + for (i = 0; i < cblocks_size; i++) {

it looks like we could set up the async write to receive the signal
with the user pointer (sigev_value.sival_ptr), which would allow us
to get the finished descriptor right away and we wouldn't need
to iterate all of them and checking on them

jirka
> + if (cblocks[i] == NULL) {
> + continue;
> + }
> + aio_errno = aio_error(cblocks[i]);
> + if (aio_errno == EINPROGRESS) {
> + do_suspend = 1;
> + continue;
> + }

SNIP

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