From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: [PATCH] PM: add statistics sysfs file for suspend to
	ram
Date: Tue, 9 Aug 2011 00:09:42 +0200
Message-ID: <201108090009.42342.rjw@sisk.pl>
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To: Pavel Machek <pavel@ucw.cz>
Cc: "Liu, ShuoX" <shuox.liu@intel.com>, yanmin_zhang@linux.intel.com, Greg KH <gregkh@suse.de>, "linux-pm@lists.linux-foundation.org" <linux-pm@lists.linux-foundation.org>, "Brown, Len" <len.brown@intel.com>
List-Id: linux-pm@vger.kernel.org

On Monday, August 08, 2011, Pavel Machek wrote:
> Hi!
> 
> > > > > > Thanks for the nice pointer. I checked dynamic debug. It's really a good debug tool.
> > > > > > With the dynamic debug:
> > > > > > 1) user need write a user space parser to process the syslog output;
> > > > > > 2) Our testing scenario is we leave the mobile for at least hours. Then, check its status.
> > > > > > No serial console available during the testing. One is because console would be suspended,
> > > > > > and the other is serial console connecting with spi or HSU devices would consume power. These
> > > > > > devices are powered off at suspend-2-ram.
> ...
> > Not in the case described by Yanmin.
> 
> Really? I see the description above.
> 
> Yes, they'd need to set up syslog to only log >= KERN_ERR, then parse
> the (small) results. Even hours worth of suspends should not cause
> _that_ many errors.
> 
> Serial console is irrelevant. You need live machine to dump dmesg, but
> again, you need live machine to access debugfs, too.

This sounds like substantial overhead to collect statistics that we can
collect at a much lower cost in the kernel.

The patch isn't very intrusive and rather straightforward.

Thanks,
Rafael