linux-kernel - Re: [PATCH RESEND] perf stat: Fix JSON output formatting in iostat

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Message-ID: <aEJnQIviayEi-Jsv@google.com>
Date: Thu, 5 Jun 2025 20:57:52 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Suchit Karunakaran <suchitkarunakaran@...il.com>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
	mark.rutland@....com, alexander.shishkin@...ux.intel.com,
	linux-perf-users@...r.kernel.org,
	linux-kernel-mentees@...ts.linux.dev, linux-kernel@...r.kernel.org,
	skhan@...uxfoundation.org
Subject: Re: [PATCH RESEND] perf stat: Fix JSON output formatting in
 iostat_prefix()

Hello,

On Thu, Jun 05, 2025 at 11:30:11PM +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.

I've tested this.  It doesn't work well.

Before:
  # ./perf iostat -j -I 1000 true
  #          time    port              0.000517525 0000:00 "Inbound Read(MB)" : "0", "Inbound Write(MB)" : "0", "Outbound Read(MB)" : "0", "Outbound Write(MB)" : "0"
       0.000517525 0000:80 
       0.000517525 0000:17 , "Inbound Read(MB)" : "0", "Inbound Write(MB)" : "0", "Outbound Read(MB)" : "0", "Outbound Write(MB)" : "0"
       0.000517525 0000:85 
       0.000517525 0000:3a , "Inbound Read(MB)" : "0", "Inbound Write(MB)" : "0", "Outbound Read(MB)" : "0", "Outbound Write(MB)" : "0"
       0.000517525 0000:ae 
       0.000517525 0000:5d , "Inbound Read(MB)" : "0", "Inbound Write(MB)" : "0", "Outbound Read(MB)" : "0", "Outbound Write(MB)" : "0"
       0.000517525 0000:d7 


After:
  # ./perf iostat -j -I 1000 true
  #          time    port         "interval" : 0.000463559, "device" : "0000:00""Inbound Read(MB)" : "0", "Inbound Write(MB)" : "0", "Outbound Read(MB)" : "0", "Outbound Write(MB)" : "0"
  "interval" : 0.000463559, "device" : "0000:80"
  "interval" : 0.000463559, "device" : "0000:17", "Inbound Read(MB)" : "0", "Inbound Write(MB)" : "0", "Outbound Read(MB)" : "0", "Outbound Write(MB)" : "0"
  "interval" : 0.000463559, "device" : "0000:85"
  "interval" : 0.000463559, "device" : "0000:3a", "Inbound Read(MB)" : "0", "Inbound Write(MB)" : "0", "Outbound Read(MB)" : "0", "Outbound Write(MB)" : "0"
  "interval" : 0.000463559, "device" : "0000:ae"
  "interval" : 0.000463559, "device" : "0000:5d", "Inbound Read(MB)" : "0", "Inbound Write(MB)" : "0", "Outbound Read(MB)" : "0", "Outbound Write(MB)" : "0"
  "interval" : 0.000463559, "device" : "0000:d7"

Thanks,
Namhyung

> 
> Signed-off-by: Suchit Karunakaran <suchitkarunakaran@...il.com>
> ---
>  tools/perf/arch/x86/util/iostat.c | 35 ++++++++++++++++++++-----------
>  1 file changed, 23 insertions(+), 12 deletions(-)
> 
> diff --git a/tools/perf/arch/x86/util/iostat.c b/tools/perf/arch/x86/util/iostat.c
> index 7442a2cd87ed..1d9c20dab5c7 100644
> --- a/tools/perf/arch/x86/util/iostat.c
> +++ b/tools/perf/arch/x86/util/iostat.c
> @@ -403,18 +403,29 @@ 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 (ts) {
> +			if (config->json_output)
> +				sprintf(prefix,
> +					"\"interval\" : %lu.%09lu, \"device\" : \"%04x:%02x\"",
> +					(unsigned long)ts->tv_sec, ts->tv_nsec,
> +					rp->domain, rp->bus);
> +			else if (config->csv_output)
> +				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, "%6lu.%09lu %04x:%02x%s",
> +					(unsigned long)ts->tv_sec, ts->tv_nsec,
> +					rp->domain, rp->bus, config->csv_sep);
> +		} else {
> +			if (config->json_output)
> +				sprintf(prefix, "\"device\" : \"%04x:%02x\"",
> +					rp->domain, rp->bus);
> +			else
> +				sprintf(prefix, "%04x:%02x%s", rp->domain,
> +					rp->bus, config->csv_sep);
> +		}
>  	}
>  }
>  
> -- 
> 2.49.0
>