2.6.22 - Suspend and Weird Load Averages

2.6.22 - Suspend and Weird Load Averages

[Parag Warudkar]

For the first time since 1997 I have a machine (Mac Mini) running a 
stock kernel which I am suspending/resuming for 2 days now without any 
problems. Amongst the various hardware and kernel versions that I've 
used so far this combination is the first to suspend/resume without issues!

But one thing that annoys me a bit is that the load averages spike up 
quite a bit after resume although it doesn't feel like the machine is 
loaded  -

Before Resume -
parag@parag-desktop:~$ uptime
 09:35:14 up  5:18,  2 users,  load average: 0.08, 0.87, 1.00
After Resume -
parag@parag-desktop:~$ uptime
 09:36:37 up  5:18,  2 users,  load average: 12.53, 3.83, 1.98
parag@parag-desktop:~$

Is this a known problem? Worth fixing?

Thanks
Parag

Re: 2.6.22 - Suspend and Weird Load Averages

[Rafael J. Wysocki]

On Wednesday, 18 July 2007 15:51, Parag Warudkar wrote:
> 
> For the first time since 1997 I have a machine (Mac Mini) running a 
> stock kernel which I am suspending/resuming for 2 days now without any 
> problems. Amongst the various hardware and kernel versions that I've 
> used so far this combination is the first to suspend/resume without issues!
> 
> But one thing that annoys me a bit is that the load averages spike up 
> quite a bit after resume although it doesn't feel like the machine is 
> loaded  -
> 
> Before Resume -
> parag@parag-desktop:~$ uptime
>  09:35:14 up  5:18,  2 users,  load average: 0.08, 0.87, 1.00
> After Resume -
> parag@parag-desktop:~$ uptime
>  09:36:37 up  5:18,  2 users,  load average: 12.53, 3.83, 1.98
> parag@parag-desktop:~$
> 
> Is this a known problem?

I think so.

This probably is due to the freezing of tasks.  Namely, the frozen tasks
are in TASK_UNINTERRUPTIBLE and add to the load average.

> Worth fixing? 

Cartainly.

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth

Re: 2.6.22 - Suspend and Weird Load Averages

[Rafael J. Wysocki]

On Wednesday, 18 July 2007 16:50, Rafael J. Wysocki wrote:
> On Wednesday, 18 July 2007 15:51, Parag Warudkar wrote:
> > 
> > For the first time since 1997 I have a machine (Mac Mini) running a 
> > stock kernel which I am suspending/resuming for 2 days now without any 
> > problems. Amongst the various hardware and kernel versions that I've 
> > used so far this combination is the first to suspend/resume without issues!
> > 
> > But one thing that annoys me a bit is that the load averages spike up 
> > quite a bit after resume although it doesn't feel like the machine is 
> > loaded  -
> > 
> > Before Resume -
> > parag@parag-desktop:~$ uptime
> >  09:35:14 up  5:18,  2 users,  load average: 0.08, 0.87, 1.00
> > After Resume -
> > parag@parag-desktop:~$ uptime
> >  09:36:37 up  5:18,  2 users,  load average: 12.53, 3.83, 1.98
> > parag@parag-desktop:~$
> > 
> > Is this a known problem?
> 
> I think so.
> 
> This probably is due to the freezing of tasks.  Namely, the frozen tasks
> are in TASK_UNINTERRUPTIBLE and add to the load average.
> 
> > Worth fixing? 
> 
> Cartainly.

s/Cartainly/Certainly/

Re: 2.6.22 - Suspend and Weird Load Averages

[Pavel Machek]

Hi!

> For the first time since 1997 I have a machine (Mac 
> Mini) running a stock kernel which I am 
> suspending/resuming for 2 days now without any problems. 
> Amongst the various hardware and kernel versions that 
> I've used so far this combination is the first to 
> suspend/resume without issues!
> 
> But one thing that annoys me a bit is that the load 
> averages spike up quite a bit after resume although it 
> doesn't feel like the machine is loaded  -
> 
> Before Resume -
> parag@parag-desktop:~$ uptime
> 09:35:14 up  5:18,  2 users,  load average: 0.08, 0.87, 
> 1.00
> After Resume -
> parag@parag-desktop:~$ uptime
> 09:36:37 up  5:18,  2 users,  load average: 12.53, 3.83, 
> 1.98
> parag@parag-desktop:~$
> 
> Is this a known problem? Worth fixing?

Known, and Rafael/Nigel have patches to fix that.

OTOH I'm not sure it is a problem -- lets just say that suspend is
hard work and therefore it raises load avg?
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: 2.6.22 - Suspend and Weird Load Averages

[Parag Warudkar]

Hi Pavel!

On 7/25/07, Pavel Machek <pavel@ucw.cz> wrote:

> Known, and Rafael/Nigel have patches to fix that.

Thanks for the info - Rafael/Nigel do you have any patches for me to
try/modify - I am just curious to see what approach the patches take
to fix this - I had started thinking about TASK_SUSPENDED which would
be equivalent to TASK_UNINTERRUPTIBLE for all purposes except load
calculation (not counted in nr_uninterruptible) but somehow I think
there might be a less intrusive / more correct way to do this.

>
> OTOH I'm not sure it is a problem -- lets just say that suspend is
> hard work and therefore it raises load avg?
>                                                        Pavel

Hehe, nope - that would be inefficient suspend for me! Any way I
understand it's purely a cosmetic problem but if we could be
cosmetically correct to report the right uptime after suspend sans the
sleep time (unlike other OSes which include sleep time when reporting
it) I think we should also fix this one to report correct load
averages.

Cheers

Parag

Re: 2.6.22 - Suspend and Weird Load Averages

[Rafael J. Wysocki]

On Wednesday, 25 July 2007 21:40, Parag Warudkar wrote:
> Hi Pavel!
> 
> On 7/25/07, Pavel Machek <pavel@ucw.cz> wrote:
> 
> > Known, and Rafael/Nigel have patches to fix that.
> 
> Thanks for the info - Rafael/Nigel do you have any patches for me to
> try/modify -

Well, I don't.

> I am just curious to see what approach the patches take 
> to fix this - I had started thinking about TASK_SUSPENDED which would
> be equivalent to TASK_UNINTERRUPTIBLE for all purposes except load
> calculation (not counted in nr_uninterruptible) but somehow I think
> there might be a less intrusive / more correct way to do this.

We wanted to save the pre-suspend load averages and restore them during the
resume.

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth

Re: 2.6.22 - Suspend and Weird Load Averages

[Pavel Machek]

On Thu 2007-07-26 14:14:22, Rafael J. Wysocki wrote:
> On Wednesday, 25 July 2007 21:40, Parag Warudkar wrote:
> > Hi Pavel!
> > 
> > On 7/25/07, Pavel Machek <pavel@ucw.cz> wrote:
> > 
> > > Known, and Rafael/Nigel have patches to fix that.
> > 
> > Thanks for the info - Rafael/Nigel do you have any patches for me to
> > try/modify -
> 
> Well, I don't.

Okay, someone did, sorry for confusion. It should be in linux-pm
archives.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html