Re: [PATCH v2] perf stat: Fix JSON output formatting in iostat_prefix()

[Namhyung Kim <namhyung@kernel.org>]

Hello,

On Sun, Jul 13, 2025 at 08:42:24PM +0530, Suchit Karunakaran wrote:
> The iostat_prefix() function previously included a TODO noting that its output
> format was incorrect in JSON mode. This patch corrects that by conditionally
> formatting the prefix string based on the output mode specified in
> perf_stat_config. Note, I didn't test it since my system doesn't support
> it.

Can any Intel folks verify this with combination of various options
like -x/-j, -I and --metric-only?

Thanks,
Namhyung

> 
> Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> ---
>  tools/perf/arch/x86/util/iostat.c | 40 +++++++++++++++++++++----------
>  1 file changed, 28 insertions(+), 12 deletions(-)
> 
> Changes since v1:
> - Fix issues in formatting
> 
> diff --git a/tools/perf/arch/x86/util/iostat.c b/tools/perf/arch/x86/util/iostat.c
> index 7442a2cd87ed..d7ae19fb83e5 100644
> --- a/tools/perf/arch/x86/util/iostat.c
> +++ b/tools/perf/arch/x86/util/iostat.c
> @@ -403,18 +403,34 @@ void iostat_prefix(struct evlist *evlist,
>  	struct iio_root_port *rp = evlist->selected->priv;
>  
>  	if (rp) {
> -		/*
> -		 * TODO: This is the incorrect format in JSON mode.
> -		 *       See prepare_timestamp()
> -		 */
> -		if (ts)
> -			sprintf(prefix, "%6lu.%09lu%s%04x:%02x%s",
> -				ts->tv_sec, ts->tv_nsec,
> -				config->csv_sep, rp->domain, rp->bus,
> -				config->csv_sep);
> -		else
> -			sprintf(prefix, "%04x:%02x%s", rp->domain, rp->bus,
> -				config->csv_sep);
> +		if (config->json_output) {
> +			if (ts) {
> +				double timestamp = ts->tv_sec + (double)ts->tv_nsec / 1e9;
> +				sprintf(prefix, "{\"interval\": %.6f, \"device\": \"%04x:%02x\", ",
> +					timestamp, rp->domain, rp->bus);
> +			} else {
> +				sprintf(prefix, "{\"device\": \"%04x:%02x\", ",
> +					rp->domain, rp->bus);
> +			}
> +		} else if (config->csv_output) {
> +			if (ts) {
> +				sprintf(prefix, "%lu.%09lu%s%04x:%02x%s",
> +					(unsigned long)ts->tv_sec, ts->tv_nsec,
> +					config->csv_sep, rp->domain, rp->bus, config->csv_sep);
> +			} else {
> +				sprintf(prefix, "%04x:%02x%s",
> +					rp->domain, rp->bus, config->csv_sep);
> +			}
> +		} else {
> +			if (ts) {
> +				sprintf(prefix, "%6lu.%09lu %04x:%02x ",
> +					(unsigned long)ts->tv_sec, ts->tv_nsec,
> +					rp->domain, rp->bus);
> +			} else {
> +				sprintf(prefix, "%04x:%02x ",
> +					rp->domain, rp->bus);
> +			}
> +		}
>  	}
>  }
>  
> -- 
> 2.50.1
>