linux-kernel - Re: [PATCH v11 3/3]: perf record: extend trace writing to multi AIO

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Date:   Mon, 8 Oct 2018 14:45:38 +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>
Subject: Re: [PATCH v11 3/3]: perf record: extend trace writing to multi AIO

On Mon, Oct 08, 2018 at 02:47:13PM +0300, Alexey Budankov wrote:
> Hi,
> 
> On 08.10.2018 13:55, Jiri Olsa wrote:
> > On Mon, Oct 08, 2018 at 09:19:17AM +0300, Alexey Budankov wrote:
> <SNIP>
> >> +#ifdef HAVE_AIO_SUPPORT
> >> +	if (!strcmp(var, "record.aio-cblocks"))
> >> +		rec->opts.nr_cblocks = strtol(value, NULL, 0);
> >> +#endif
> >>  
> >>  	return 0;
> >>  }
> >> @@ -1837,6 +1864,10 @@ static struct option __record_options[] = {
> >>  			  "signal"),
> >>  	OPT_BOOLEAN(0, "dry-run", &dry_run,
> >>  		    "Parse options then exit"),
> >> +#ifdef HAVE_AIO_SUPPORT
> >> +	OPT_INTEGER(0, "aio-cblocks", &record.opts.nr_cblocks,
> >> +		    "Max number of simultaneous per-mmap trace writes (default: 0 - serial, max: 4)"),
> >> +#endif
> > 
> > could you please move the option to enable that to the previou patch?
> > so we could test the simple variant as well
> 
> Ok.
> 
> > 
> > also I think it'd be better if we have simple '--aio' option that would
> > enable this with some default values..  and add --aio-cblocks to configure
> > that further
> 
> Well, absence of --aio option, on the command line or in .perfconfig, or --aio=0 
> means serial writing.
> 
> From this perspective perf record --aio --aio-cblocks=N looks like a complication.

'perf record --aio-cblocks=N' could imply '--aio',

I'd like to have simple/intuitive way to enable that,
without studing the meaning of the cblocks argument

  # perf record --aio ...

means that I'm storing data via async writes,
and using some reasonable default for cblocks

and later on we'd add 'perf record --threads'
allowing threads based writers ;-)

jirka