linux-kernel - Re: Intel graphics CPU usage

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Date:	Mon, 16 Aug 2010 13:30:08 +1000
From:	Dave Airlie <airlied@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Dave Airlie <airlied@...ux.ie>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Zhao Yakui <yakui.zhao@...el.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Adam Jackson <ajax@...hat.com>, linux-kernel@...r.kernel.org,
	DRI mailing list <dri-devel@...ts.freedesktop.org>
Subject: Re: Intel graphics CPU usage - SDVO detect bogosity?

On Sun, 2010-08-15 at 19:32 -0700, Linus Torvalds wrote:
> I started wondering why 'top' was showing an otherwise idle system as
> having a load average of 0.5+, and worker threads constantly using the
> CPU.
> 
> So I did a system-wide profile, and got the attached output (look at
> it in a really wide terminal).
> 
> There seems to be something _seriously_ wrong with i915 SDVO detect.
> This is on an Apple Mac Mini (hey, your favorite problem child!), and
> apparently it spends 20% of its non-idle CPU time just doing udelay's
> for the i2c SDVO connection detection.
> 
> That sounds a bit wrong, doesn't it?

At least we should replace mdelay with msleep in those functions.

Can you get a boot with drm.debug=4?

I wonder are we picking up a bad SDVO, the insane code retries 50 times
with a hard loop delay.

Dave.


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