linux-kernel - idle=poll burns my box [was Re: 2.6.22-rc2-mm1]

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Date:	Fri, 25 May 2007 23:20:25 +0200
From:	"J.A. Magallón" <jamagallon@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: idle=poll burns my box [was Re: 2.6.22-rc2-mm1]

On Wed, 23 May 2007 00:42:33 -0700, Andrew Morton <akpm@...ux-foundation.org> wrote:

> 
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc2/2.6.22-rc2-mm1/
> 

Don't know if it's specific to this kernel, but as I have realized it now...

I booted with idle=poll to check some issues (with nvidia driver, btw).
And suddenly I noticed my box was running near 80ºC hot.
I pulled out the lid, an try to see what happened.

In short, idle=poll rises the temperature about 20ºC.
I have an ASUS PC-DL mobo, with a couple Xeon Northwood with HypertThreading
at 2.4 GHz, for a total of 4 threads.

If I boot the box with idle=poll, and let it doing _nothing_ but staring at
the gnome desktop, I get this temperatures:
(Time,VRM,CPU0,CPU1) (wihtout the side cover, remember...)

15:46 64 56 54
15:55 70 60 56
16:02 71 62 57

If I reboot without idle=poll, the box colds quickly:

16:07 58 52 48
16:12 50 43 42
16:15 49 42 41

I I put the box to do some multithreaded render, so all four cores stay
above 98% usage, the box warms again:

16:17 51 43 42
16:24 67 57 54
16:28 70 60 56
16:30 72 61 57
16:37 72 61 56

And as soon as I stop the work, it colds again:

16:41 71 60 56
16:42 64 56 52
16:43 60 54 50
16:45 55 48 46
16:46 53 46 44

Left alone for awhile, it stays at 46 39 39 (for VRM and both CPUs, as I said).

Is idle=poll a quick and dirty way to burn your box in flames ?
To warm your cpu doing nothing ?
Summer is coming, but this...

Any ideas ?

--
J.A. Magallon <jamagallon()ono!com>     \               Software is like sex:
                                         \         It's better when it's free
Mandriva Linux release 2008.0 (Cooker) for i586
Linux 2.6.21-jam03 (gcc 4.1.2 20070302 (4.1.2-1mdv2007.1)) SMP PREEMPT
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
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