linux-kernel - Re: [RFC PATCH] power: Add option to log time spent in suspend

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Date:	Wed, 1 May 2013 02:29:29 +0200
From:	Pavel Machek <pavel@....cz>
To:	Zoran Markovic <zoran.markovic@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	Colin Cross <ccross@...roid.com>,
	Android Kernel Team <kernel-team@...roid.com>,
	Todd Poynor <toddpoynor@...gle.com>,
	San Mehat <san@...gle.com>, Benoit Goby <benoit@...roid.com>,
	John Stultz <john.stultz@...aro.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Len Brown <len.brown@...el.com>
Subject: Re: [RFC PATCH] power: Add option to log time spent in suspend

Hi!

> From: Colin Cross <ccross@...roid.com>
> 
> Below is a patch from android kernel that maintains a histogram of
> suspend times. Please review and provide feedback.
> 
> Prints the time spent in suspend in the kernel log, and keeps statistics
> on the time spent in suspend in /sys/kernel/debug/suspend_time
> 
> Cc: Android Kernel Team <kernel-team@...roid.com>
> Cc: Colin Cross <ccross@...roid.com>
> Cc: Todd Poynor <toddpoynor@...gle.com>
> Cc: San Mehat <san@...gle.com>
> Cc: Benoit Goby <benoit@...roid.com>
> Cc: John Stultz <john.stultz@...aro.org>
> Cc: Pavel Machek <pavel@....cz>
> Cc: Rafael J. Wysocki <rjw@...k.pl>
> Cc: Len Brown <len.brown@...el.com>
> Signed-off-by: Colin Cross <ccross@...roid.com>
> Signed-off-by: Todd Poynor <toddpoynor@...gle.com>
> [zoran.markovic@...aro.org: Re-formatted suspend time table to better fit
> expected values, tweaked commit message]
> Signed-off-by: Zoran Markovic <zoran.markovic@...aro.org>

> +++ b/kernel/power/suspend_time.c
> @@ -0,0 +1,111 @@
> +/*
> + * debugfs file to track time spent in suspend
> + *
> + * Copyright (c) 2011, Google, Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + */
> +
> +#include <linux/debugfs.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/seq_file.h>
> +#include <linux/syscore_ops.h>
> +#include <linux/time.h>
> +
> +static struct timespec suspend_time_before;
> +static unsigned int time_in_suspend_bins[32];
> +
> +#ifdef CONFIG_DEBUG_FS
> +static int suspend_time_debug_show(struct seq_file *s, void *data)
> +{
> +	unsigned int bin;
> +	seq_printf(s, "      time (secs)        count\n");
> +	seq_printf(s, "------------------------------\n");
> +	for (bin = 0; bin < 32; bin++) {
> +		if (time_in_suspend_bins[bin] == 0)
> +			continue;
> +		seq_printf(s, "%10u - %-10u %4u\n",
> +			bin ? 1 << (bin - 1) : 0, 1 << bin,
> +				time_in_suspend_bins[bin]);
> +	}
> +	return 0;
> +}
> +
> +static int suspend_time_debug_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, suspend_time_debug_show, NULL);
> +}

Ok, whole new driver to get timing info... As we already have times in
printk, can't existing printks() get the same info? Maybe
Documentation/ file describing how to get that info from dmesg would
be enough?
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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