linux-kernel - Re: [PATCH v2 12/15] perf record: introduce thread local variable for trace streaming

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Message-ID: <20201024154357.GD2589351@krava>
Date:   Sat, 24 Oct 2020 17:43:57 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 12/15] perf record: introduce thread local variable
 for trace streaming

On Wed, Oct 21, 2020 at 07:07:00PM +0300, Alexey Budankov wrote:
> 
> Introduce thread local variable and use it for threaded trace streaming.
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
> ---
>  tools/perf/builtin-record.c | 71 ++++++++++++++++++++++++++++++++-----
>  1 file changed, 62 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 89cb8e913fb3..3b7e9026f25b 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -101,6 +101,8 @@ struct thread_data {
>  	u64		   bytes_written;
>  };
>  
> +static __thread struct thread_data *thread;
> +
>  struct record {
>  	struct perf_tool	tool;
>  	struct record_opts	opts;
> @@ -587,7 +589,11 @@ static int record__pushfn(struct mmap *map, void *to, void *bf, size_t size)
>  		}
>  	}
>  
> -	rec->samples++;
> +	if (thread)
> +		thread->samples++;
> +	else
> +		rec->samples++;

this is really wrong, let's keep just single samples counter
ditto for all the other places in this patch

SNIP

> -		if (hits == rec->samples) {
> +		if (thread)
> +			hits1 = thread->samples;
> +		else
> +			hits1 = rec->samples;
> +
> +		if (hits0 == hits1) {
>  			if (done || draining)
>  				break;
> -			err = evlist__poll(rec->evlist, -1);
> +
> +			if (thread)
> +				err = fdarray__poll(&thread->pollfd, -1);
> +			else
> +				err = evlist__poll(rec->evlist, -1);

same here, why do we have the __thread struct then?

jirka