Received-SPF: pass (google.com: domain of linux-kernel+bounces-79480-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Fri, 23 Feb 2024 22:02:50 -0800
From: "Darrick J. Wong" <djwong@kernel.org>
To: Kent Overstreet <kent.overstreet@linux.dev>
Cc: akpm@linux-foundation.org, daniel@gluo.nz, linux-xfs@vger.kernel.org,
	linux-bcachefs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 09/10] time_stats: report information in json format
Message-ID: <20240224060250.GQ6226@frogsfrogsfrogs>
References: <170873667916.1860949.11027844260383646446.stgit@frogsfrogsfrogs>
 <170873668085.1860949.11659237532415596101.stgit@frogsfrogsfrogs>
 <20240224041545.GC616564@frogsfrogsfrogs>
 <hf4u56xx3riqz2wyx3qxqiidccocu6cs5z5qdla3zgo5v3wcbl@dldlaaamx2kn>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <hf4u56xx3riqz2wyx3qxqiidccocu6cs5z5qdla3zgo5v3wcbl@dldlaaamx2kn>

On Sat, Feb 24, 2024 at 12:10:33AM -0500, Kent Overstreet wrote:
> On Fri, Feb 23, 2024 at 08:15:45PM -0800, Darrick J. Wong wrote:
> > On Fri, Feb 23, 2024 at 05:12:26PM -0800, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <djwong@kernel.org>
> > > 
> > > Export json versions of time statistics information.  Given the tabular
> > > nature of the numbers exposed, this will make it a lot easier for higher
> > > (than C) level languages (e.g. python) to import information without
> > > needing to write yet another clumsy string parser.
> > > 
> > > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > > Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
> > > ---
> > >  include/linux/time_stats.h |    2 +
> > >  lib/time_stats.c           |   87 ++++++++++++++++++++++++++++++++++++++++++++
> > >  2 files changed, 89 insertions(+)
> > > 
> > > 
> > > diff --git a/include/linux/time_stats.h b/include/linux/time_stats.h
> > > index b3c810fff963a..4e1f5485ed039 100644
> > > --- a/include/linux/time_stats.h
> > > +++ b/include/linux/time_stats.h
> > > @@ -156,6 +156,8 @@ static inline bool track_event_change(struct time_stats *stats, bool v)
> > >  struct seq_buf;
> > >  void time_stats_to_seq_buf(struct seq_buf *, struct time_stats *,
> > >  		const char *epoch_name, unsigned int flags);
> > > +void time_stats_to_json(struct seq_buf *, struct time_stats *,
> > > +		const char *epoch_name, unsigned int flags);
> > >  
> > >  void time_stats_exit(struct time_stats *);
> > >  void time_stats_init(struct time_stats *);
> > > diff --git a/lib/time_stats.c b/lib/time_stats.c
> > > index 0fb3d854e503b..c0f209dd9f6dd 100644
> > > --- a/lib/time_stats.c
> > > +++ b/lib/time_stats.c
> > > @@ -266,6 +266,93 @@ void time_stats_to_seq_buf(struct seq_buf *out, struct time_stats *stats,
> > >  }
> > >  EXPORT_SYMBOL_GPL(time_stats_to_seq_buf);
> > >  
> > > +void time_stats_to_json(struct seq_buf *out, struct time_stats *stats,
> > > +		const char *epoch_name, unsigned int flags)
> > > +{
> > > +	struct quantiles *quantiles = time_stats_to_quantiles(stats);
> > > +	s64 f_mean = 0, d_mean = 0;
> > > +	u64 f_stddev = 0, d_stddev = 0;
> > > +
> > > +	if (stats->buffer) {
> > > +		int cpu;
> > > +
> > > +		spin_lock_irq(&stats->lock);
> > > +		for_each_possible_cpu(cpu)
> > > +			__time_stats_clear_buffer(stats, per_cpu_ptr(stats->buffer, cpu));
> > > +		spin_unlock_irq(&stats->lock);
> > > +	}
> > > +
> > > +	if (stats->freq_stats.n) {
> > > +		/* avoid divide by zero */
> > > +		f_mean = mean_and_variance_get_mean(stats->freq_stats);
> > > +		f_stddev = mean_and_variance_get_stddev(stats->freq_stats);
> > > +		d_mean = mean_and_variance_get_mean(stats->duration_stats);
> > > +		d_stddev = mean_and_variance_get_stddev(stats->duration_stats);
> > > +	} else if (flags & TIME_STATS_PRINT_NO_ZEROES) {
> > > +		/* unless we didn't want zeroes anyway */
> > > +		return;
> > > +	}
> > > +
> > > +	seq_buf_printf(out, "{\n");
> > > +	seq_buf_printf(out, "  \"epoch\":       \"%s\",\n", epoch_name);
> > > +	seq_buf_printf(out, "  \"count\":       %llu,\n", stats->duration_stats.n);
> > > +
> > > +	seq_buf_printf(out, "  \"duration_ns\": {\n");
> > > +	seq_buf_printf(out, "    \"min\":       %llu,\n", stats->min_duration);
> > > +	seq_buf_printf(out, "    \"max\":       %llu,\n", stats->max_duration);
> > > +	seq_buf_printf(out, "    \"total\":     %llu,\n", stats->total_duration);
> > > +	seq_buf_printf(out, "    \"mean\":      %llu,\n", d_mean);
> > > +	seq_buf_printf(out, "    \"stddev\":    %llu\n", d_stddev);
> > > +	seq_buf_printf(out, "  },\n");
> > > +
> > > +	d_mean = mean_and_variance_weighted_get_mean(stats->duration_stats_weighted, TIME_STATS_MV_WEIGHT);
> > > +	d_stddev = mean_and_variance_weighted_get_stddev(stats->duration_stats_weighted, TIME_STATS_MV_WEIGHT);
> > > +
> > > +	seq_buf_printf(out, "  \"duration_ewma_ns\": {\n");
> > > +	seq_buf_printf(out, "    \"mean\":      %llu,\n", d_mean);
> > > +	seq_buf_printf(out, "    \"stddev\":    %llu\n", d_stddev);
> > > +	seq_buf_printf(out, "  },\n");
> > > +
> > > +	seq_buf_printf(out, "  \"frequency_ns\": {\n");
> > 
> > I took the variable names too literally here; these labels really ought
> > to be "between_ns" and "between_ewma_ns" to maintain consistency with
> > the labels in the table format.
> > 
> > > +	seq_buf_printf(out, "    \"min\":       %llu,\n", stats->min_freq);
> > > +	seq_buf_printf(out, "    \"max\":       %llu,\n", stats->max_freq);
> > > +	seq_buf_printf(out, "    \"mean\":      %llu,\n", f_mean);
> > > +	seq_buf_printf(out, "    \"stddev\":    %llu\n", f_stddev);
> > > +	seq_buf_printf(out, "  },\n");
> > > +
> > > +	f_mean = mean_and_variance_weighted_get_mean(stats->freq_stats_weighted, TIME_STATS_MV_WEIGHT);
> > > +	f_stddev = mean_and_variance_weighted_get_stddev(stats->freq_stats_weighted, TIME_STATS_MV_WEIGHT);
> > > +
> > > +	seq_buf_printf(out, "  \"frequency_ewma_ns\": {\n");
> > > +	seq_buf_printf(out, "    \"mean\":      %llu,\n", f_mean);
> > > +	seq_buf_printf(out, "    \"stddev\":    %llu\n", f_stddev);
> > > +
> > > +	if (quantiles) {
> > > +		u64 last_q = 0;
> > > +
> > > +		/* close frequency_ewma_ns but signal more items */
> > 
> > (also this comment)
> > 
> > > +		seq_buf_printf(out, "  },\n");
> > > +
> > > +		seq_buf_printf(out, "  \"quantiles_ns\": [\n");
> > > +		eytzinger0_for_each(i, NR_QUANTILES) {
> > > +			bool is_last = eytzinger0_next(i, NR_QUANTILES) == -1;
> > > +
> > > +			u64 q = max(quantiles->entries[i].m, last_q);
> > > +			seq_buf_printf(out, "    %llu", q);
> > > +			if (!is_last)
> > > +				seq_buf_printf(out, ", ");
> > > +			last_q = q;
> > > +		}
> > > +		seq_buf_printf(out, "  ]\n");
> > > +	} else {
> > > +		/* close frequency_ewma_ns without dumping further */
> > 
> > (this one too)
> > 
> > Kent, would you mind making that edit the next time you reflow your
> > branch?
> > 
> > --D
> > 
> > > +		seq_buf_printf(out, "  }\n");
> > > +	}
> > > +
> > > +	seq_buf_printf(out, "}\n");
> > > +}
> > > +EXPORT_SYMBOL_GPL(time_stats_to_json);
> > > +
> > >  void time_stats_exit(struct time_stats *stats)
> > >  {
> > >  	free_percpu(stats->buffer);
> > > 
> > > 
> 
> 
> From 5885a65fa5a0aace7bdf1a8fa58ac2bca3b15900 Mon Sep 17 00:00:00 2001
> From: Kent Overstreet <kent.overstreet@linux.dev>
> Date: Sat, 24 Feb 2024 00:10:06 -0500
> Subject: [PATCH] fixup! time_stats: report information in json format
> 
> 
> diff --git a/lib/time_stats.c b/lib/time_stats.c
> index 0b90c80cba9f..d7dd64baebb8 100644
> --- a/lib/time_stats.c
> +++ b/lib/time_stats.c
> @@ -313,7 +313,7 @@ void time_stats_to_json(struct seq_buf *out, struct time_stats *stats,
>  	seq_buf_printf(out, "    \"stddev\":    %llu\n", d_stddev);
>  	seq_buf_printf(out, "  },\n");
>  
> -	seq_buf_printf(out, "  \"frequency_ns\": {\n");
> +	seq_buf_printf(out, "  \"between_ns\": {\n");
>  	seq_buf_printf(out, "    \"min\":       %llu,\n", stats->min_freq);
>  	seq_buf_printf(out, "    \"max\":       %llu,\n", stats->max_freq);
>  	seq_buf_printf(out, "    \"mean\":      %llu,\n", f_mean);
> @@ -323,14 +323,14 @@ void time_stats_to_json(struct seq_buf *out, struct time_stats *stats,
>  	f_mean = mean_and_variance_weighted_get_mean(stats->freq_stats_weighted, TIME_STATS_MV_WEIGHT);
>  	f_stddev = mean_and_variance_weighted_get_stddev(stats->freq_stats_weighted, TIME_STATS_MV_WEIGHT);
>  
> -	seq_buf_printf(out, "  \"frequency_ewma_ns\": {\n");
> +	seq_buf_printf(out, "  \"between_ewma_ns\": {\n");

Looks good to me,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

>  	seq_buf_printf(out, "    \"mean\":      %llu,\n", f_mean);
>  	seq_buf_printf(out, "    \"stddev\":    %llu\n", f_stddev);
>  
>  	if (quantiles) {
>  		u64 last_q = 0;
>  
> -		/* close frequency_ewma_ns but signal more items */
> +		/* close between_ewma_ns but signal more items */
>  		seq_buf_printf(out, "  },\n");
>  
>  		seq_buf_printf(out, "  \"quantiles_ns\": [\n");
> @@ -345,7 +345,7 @@ void time_stats_to_json(struct seq_buf *out, struct time_stats *stats,
>  		}
>  		seq_buf_printf(out, "  ]\n");
>  	} else {
> -		/* close frequency_ewma_ns without dumping further */
> +		/* close between_ewma_ns without dumping further */
>  		seq_buf_printf(out, "  }\n");
>  	}
>