linux-kernel - RE: [REGRESSION] 774ac8b7eff6 ("Thermal: initialize thermal zone device correctly") causes performance drop

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Date:	Thu, 17 Mar 2016 00:17:07 +0000
From:	"Zhang, Rui" <rui.zhang@...el.com>
To:	Laura Abbott <labbott@...hat.com>,
	Javi Merino <javi.merino@....com>,
	"Chen, Yu C" <yu.c.chen@...el.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Manuel Krause <manuelkrause@...scape.net>,
	szegad <szegadlo@...zta.onet.pl>, prash <prash.n.rao@...il.com>,
	amish <ammdispose-arch@...oo.com>,
	Matthias <morpheusxyz123@...oo.de>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: RE: [REGRESSION] 774ac8b7eff6 ("Thermal: initialize thermal zone
 device correctly") causes performance drop

Can you send me the output of "grep . /sys/class/thermal/*/*" both w/ and w/o the broken patch series?

Thanks,
rui

> -----Original Message-----
> From: Laura Abbott [mailto:labbott@...hat.com]
> Sent: Thursday, March 17, 2016 6:28 AM
> To: Zhang, Rui <rui.zhang@...el.com>; Javi Merino <javi.merino@....com>;
> Chen, Yu C <yu.c.chen@...el.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Manuel Krause
> <manuelkrause@...scape.net>; szegad <szegadlo@...zta.onet.pl>; prash
> <prash.n.rao@...il.com>; amish <ammdispose-arch@...oo.com>; Matthias
> <morpheusxyz123@...oo.de>; linux-pm@...r.kernel.org; Linux Kernel
> Mailing List <linux-kernel@...r.kernel.org>
> Subject: [REGRESSION] 774ac8b7eff6 ("Thermal: initialize thermal zone device
> correctly") causes performance drop
> Importance: High
> 
> Hi,
> 
> Fedora received a bug report
> (https://bugzilla.redhat.com/show_bug.cgi?id=1317190)
> of a major performance drop on various bench marks and general system
> sluggishness with the 4.4.4 kernel update. The benchmarks were showing a
> reduction to about 18% performance (not minor).
> 
> Bisection showed the first bad commit was
> 
> commit 774ac8b7eff69e0786970157de2157e68b22f456
> Author: Zhang Rui <rui.zhang@...el.com>
> Date:   Fri Oct 30 16:31:47 2015 +0800
> 
>      Thermal: initialize thermal zone device correctly
> 
>      commit bb431ba26c5cd0a17c941ca6c3a195a3a6d5d461 upstream.
> 
>      After thermal zone device registered, as we have not read any
>      temperature before, thus tz->temperature should not be 0,
>      which actually means 0C, and thermal trend is not available.
>      In this case, we need specially handling for the first
>      thermal_zone_device_update().
> 
>      Both thermal core framework and step_wise governor is
>      enhanced to handle this. And since the step_wise governor
>      is the only one that uses trends, so it's the only thermal
>      governor that needs to be updated.
> 
>      Tested-by: Manuel Krause <manuelkrause@...scape.net>
>      Tested-by: szegad <szegadlo@...zta.onet.pl>
>      Tested-by: prash <prash.n.rao@...il.com>
>      Tested-by: amish <ammdispose-arch@...oo.com>
>      Tested-by: Matthias <morpheusxyz123@...oo.de>
>      Reviewed-by: Javi Merino <javi.merino@....com>
>      Signed-off-by: Zhang Rui <rui.zhang@...el.com>
>      Signed-off-by: Chen Yu <yu.c.chen@...el.com>
>      Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> 
> 
> Reverting this plus to other commits in the series (a67208e94d94
> "Thermal: handle thermal zone device properly during system sleep"
> and 27f356149d59 "Thermal: do thermal zone update after a cooling device
> registered") confirmed the performance was back to normal.
> 
> Bugzilla has the full discussion but this comment from one of the reporters
> sums it up:
> 
> "In 4.4.3 and prior, my 2.40 MHz processor would fluctuate between
> 1000 and 3400 MHz.  In 4.4.4, the processor would fluctuate between
> 400 and 700 MHz, according to /proc/cpuinfo.
> 
> Setting /sys/devices/system/cpu/cpufreq/policy0/scaling_governor to
> performance, instead of the default "powersave" forces the CPU to
> 2400 MHz, and improves performance greatly, but still not to the same level
> as in 4.4.3."
> 
> Any ideas?
> 
> Thanks,
> Laura