Re: [PATCH v13 3/3]: perf record: extend trace writing to multi AIO

[Namhyung Kim]

Hi,

On Thu, Oct 11, 2018 at 09:59:19PM +0300, Alexey Budankov wrote:
> 
> Multi AIO trace writing allows caching more kernel data into userspace 
> memory postponing trace writing for the sake of overall profiling data 
> thruput increase. It could be seen as kernel data buffer extension into
> userspace memory.
> 
> With aio option value different from 0, default value is 1, 
> tool has capability to cache more and more data into user space
> along with delegating spill to AIO.
> 
> That allows avoiding suspend at record__aio_sync() between calls of 
> record__mmap_read_evlist() and increase profiling data thruput for 
> the cost of userspace memory.
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
> ---
> Changes in v13:
> - preserved --aio option name avoiding complication
> Changes in v12:
> - extended --aio option to --aio-cblocks=<n>
> Changes in v10:
> - added description of aio-cblocks option into perf-record.txt
> ---

[SNIP]
> @@ -1882,8 +1913,8 @@ static struct option __record_options[] = {
>  	OPT_BOOLEAN(0, "dry-run", &dry_run,
>  		    "Parse options then exit"),
>  #ifdef HAVE_AIO_SUPPORT
> -	OPT_CALLBACK_NOOPT(0, "aio", &record.opts,
> -		     NULL, "Enable asynchronous trace writing mode",
> +	OPT_CALLBACK(0, "aio", &record.opts,
> +		     "n", "Use <n> control blocks in asynchronous trace writing mode (default: 1, max: 4)",

One question.  It seems you used a very large N in your test result.
Why did you limit it to 4 here?  Is it something different?  Maybe
you'd better making it a macro constant for future changes..

Otherwise looks good to me.  For the 3 patches

Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>

Thanks,
Namhyung



>  		     record__aio_parse),
>  #endif
>  	OPT_END()
> @@ -2078,6 +2109,8 @@ int cmd_record(int argc, const char **argv)
>  		goto out;
>  	}
>  
> +	if (rec->opts.nr_cblocks > 4)
> +		rec->opts.nr_cblocks = 4;
>  	if (verbose > 0)
>  		pr_info("nr_cblocks: %d\n", rec->opts.nr_cblocks);