Messages in this thread | | | Date | Mon, 14 Jun 2010 14:42:44 -0400 | From | Nick Bowler <> | Subject | Re: Why is kslowd accumulating so much CPU time? |
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On 06:00 Mon 14 Jun , Dave Airlie wrote: > On Mon, Jun 14, 2010 at 5:49 AM, <tytso@mit.edu> wrote: > > It's a Lenovo T400, with an Intel GPU: > > [...] > > Why does KMS need to poll so frequently? 40 minutes of CPU time > > accumulated in 4 hours of uptime translates to 16% of the CPU being > > consumed by kslowd daemons, which seems... excessive. > > [...] > > I have the following patch which I'm going to install later tonight to > > see if I can figure out if it really is drm_crtc_helper.c which is > > really responsible for all of the kslowd time being burned, but an > > examination of the source doesn't seem to show any other that I'm > > using that would likely be using the slow workqueue. > > It most likely is, but polling shouldn't really be taking huge amounts > of CPU, unless there are some u/mdelays in there which would be bad. > > In theory on Intel with hotplug irqs we shouldn't be poilling at all, > I must check why, the other thing is you could be suffering from the > hotplug irq problem that others have reported, this would cause slow > work triggers which aren't part of the normal poll cycle.
This sounds exactly like the issue I've been seeing on a T500 laptop, as well (GM45 board). The slowdowns render the system essentially unusable, as it can spend a loooong time just moving the mouse cursor a few pixels on the screen. During this time, nothing else on the display is updating (glxgears drops to 0fps). Things generally seem to be working fine if I am not moving the mouse, or if I'm not running X.
I do not have this issue on a desktop machine with a G45.
Unfortunately, bisection is proving difficult because the exact set of conditions to trigger the problems seem to be eluding me: sometimes the kernel will work perfectly fine for quite some time, and then go downhill from there. However, this is definitely a regression introduced after 2.6.35-rc1.
-- Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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