linux-kernel - Re: [PATCH v1 2/2]: perf record: enable asynchronous trace writing

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Date:   Sun, 26 Aug 2018 23:48:56 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v1 2/2]: perf record: enable asynchronous trace writing

On Tue, Aug 21, 2018 at 11:27:03AM +0300, Alexey Budankov wrote:

SNIP

> -static int record__pushfn(void *to, void *bf, size_t size)
> +static int record__pushfn(void *to, void *bf, size_t size, off_t off)
>  {
>  	struct record *rec = to;
> +	struct perf_mmap *map = bf;
>  
>  	rec->samples++;
> -	return record__write(rec, bf, size);
> +	return record__aio_write(rec->session->data->file.fd, &map->cblock,
> +			map->data, size, off);
>  }
>  
>  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 * 500  * 1 };
> +
> +	if (!cblocks_size)
> +		return 0;
> +
> +	do {
> +		do_suspend = 0;
> +		nanosleep(&timeoutS, NULL);

why the extra sleep in here and not sleeping through aio_suspend call?

jirka

> +		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");

SNIP