linux-kernel - Re: [PATCH V2 4/5] perf record: synthesize event multithreading support

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Message-ID: <20171018153759.GB512@krava>
Date:   Wed, 18 Oct 2017 17:37:59 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     kan.liang@...el.com
Cc:     acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
        peterz@...radead.org, jolsa@...nel.org, wangnan0@...wei.com,
        hekuang@...wei.com, namhyung@...nel.org,
        alexander.shishkin@...ux.intel.com, adrian.hunter@...el.com,
        ak@...ux.intel.com
Subject: Re: [PATCH V2 4/5] perf record: synthesize event multithreading
 support

On Wed, Oct 18, 2017 at 07:29:32AM -0700, kan.liang@...el.com wrote:

SNIP

> +static int record__multithread_synthesize(struct record *rec,
> +					  struct machine *machine,
> +					  struct perf_tool *tool,
> +					  struct record_opts *opts)
> +{
> +	int i, err, nr_thread = sysconf(_SC_NPROCESSORS_ONLN);
> +	char name[PATH_MAX];
> +	struct stat st;
> +
> +	if (nr_thread <= 1)
> +		return __machine__synthesize_threads(machine, tool,
> +						     &opts->target,
> +						     rec->evlist->threads,
> +						     process_synthesized_event,
> +						     opts->sample_address,
> +						     opts->proc_map_timeout,
> +						     1);
> +
> +	rec->synthesized_file = calloc(nr_thread, sizeof(struct perf_data_file));
> +	if (rec->synthesized_file == NULL) {
> +		pr_debug("Could not do multithread synthesize."
> +			 "Roll back to single thread\n");
> +		nr_thread = 1;

I guess we could fail here anyway.. it'd simplify the code below ;-)

jirka

> +	} else {
> +		perf_set_multithreaded();
> +		for (i = 0; i < nr_thread; i++) {
> +			snprintf(name, sizeof(name), "%s.%d",
> +				 SYNTHESIZED_PATH, i);
> +			rec->synthesized_file[i].path = name;
> +			err = perf_data_file__open(&rec->synthesized_file[i]);
> +			if (err) {
> +				pr_err("Failed to open file %s\n",
> +				       rec->synthesized_file[i].path);
> +				goto free;
> +			}
> +		}
> +	}
> +
> +	err = __machine__synthesize_threads(machine, tool, &opts->target,
> +					    rec->evlist->threads,
> +					    process_synthesized_event,
> +					    opts->sample_address,
> +					    opts->proc_map_timeout, nr_thread);
> +	if (err < 0)
> +		goto free;
> +
> +	if (nr_thread > 1) {
> +		int fd_from, fd_to;
> +
> +		fd_to = rec->session->file->fd;
> +		for (i = 0; i < nr_thread; i++) {
> +			fd_from = rec->synthesized_file[i].fd;
> +
> +			fstat(fd_from, &st);
> +			if (st.st_size == 0)
> +				continue;
> +			err = copyfile_offset(fd_from, 0, fd_to,
> +					      lseek(fd_to, 0, SEEK_END),
> +					      st.st_size);
> +			update_bytes_written(rec, st.st_size);
> +		}
> +	}
> +
> +free:
> +	if (nr_thread > 1) {
> +		for (i = 0; i < nr_thread; i++) {
> +			if (rec->synthesized_file[i].fd > 0)
> +				perf_data_file__close(&rec->synthesized_file[i]);
> +		}
> +		free(rec->synthesized_file);
> +		perf_set_singlethreaded();
> +	}
> +
> +	return err;
> +}

SNIP