[SOLVED] Short and random CPU spikes only in X

falconindy · 2011-01-10 14:06:49

I built myself a new system over the weekend, and everything has been going swimmingly aside from one unsolved issue I've been experiencing within X. At seemingly random intervals, CPU usage spikes on a single core to anywhere between 20-50% and redraw on apps becomes choppy (e.g. during scrolling via either mouse or keyboard). Even while SSH'd in, the spikes are noticeable until I kill X (I'm not forwarding X, just hooking into my tmux session). During this time, it's only X which is consuming CPU. Relevant hardware specs:

- Asus P6X58D-E motherboard (bios is up to date)
- Intel core i7 980x
- 12gb g.skill ddr3 1600mhz RAM (default XMP profile)
- eVGA nvidia 450 GTS graphics card

So far, I've tried:

- switching kernels. Both downgrading to 2.6.36 as well as building a custom 2.6.37 kernel. no effect.
- switching video drivers. nouveau still shows this issue
- switching video cards. my old BFG nvidia 8600 GTS which (still) works great on my old rig shows the same issue.
- downgrading to extra/xorg-server
- disabling speedstep/turbo boost. nada.

Google returns nothing specific to any of my hardware aside from a few notes about X58 chipset support being a little young (and an equal number of reports saying X58 boards are running fine). The system is 100% stable and absurdly happy outside of X. I'm running out of ideas on where to look. Anyone know where I should be poking around next?

Last edited by falconindy (2011-01-18 04:39:00)

Julius2 · 2011-01-10 14:21:51

Seems like a nice system, and it looks like you bought the same RAM I did (albeit twice as much per DIMM). The 980X looks like a bit of overkill -- what must it have been, $1000?

I had this issue several years ago when I was using catalyst with XFCE. It turned out to be (somewhat) the fault of the window manager, or at least the way it and X11 and the graphics driver were interacting. I forget what I did to fix it. What window manager are you using?

falconindy · 2011-01-10 14:26:19

Yes, I realize it's overkill. It was a fun build, and it serves its purpose.

Currently using DWM. I guess I had it on my list to try a different tiler but I was suspicious that this could be the cause of it.

Julius2 · 2011-01-11 14:16:06

My guess is that it's something related to something specific that is running or the way that the graphics drivers are working with your particular card. Considering that it's a fairly new one, driver support on even nvidia might be weak, and I doubt nouveau would be any better. All I can suggest is that you investigate that particular card and its behaviour under Linux and see if anyone has had a similar problem and solved it.

falconindy · 2011-01-11 16:00:53

As I mentioned, switching cards has no effect. My old 8600 GTS exhibits the same issue.

more testing...
- tried openbox and fluxbox. Same issue. Ruling out the window manager.
- I underclocked my RAM to 1333mhz and looser timings. No change. Still can't rule this out 100%, but I'm taking it off the table because everything else other than X is stable.
- iotop shows no significant access coinciding with the CPU spikes.
- as far as i can tell, /proc/interrupts doesn't show anything out of the ordinary. i could be wrong here, but it seemed roughly in line with my old box and a VM i spun up.

I'm away from home until next monday... plenty of time to dwell on what else this isn't related to.

falconindy · 2011-01-18 04:38:50

This story has a happy ending.

Here's a list of things that didn't work:
- Enabling ACPI 2.0 in the BIOS
- Moving my graphics card to another PCI-E slot
- Rebuilding many kernels
- Reformatting my root as ext4
- Replacing ALSA with OSS
- Loading the latest microcode from intel (though there are reports of "unexpected behavior" on the 980x without it)
- Staring at strace output of X
- Building more kernels
- dancing naked around a ceremonial fire, drinking chicken blood and speaking in tongues
- Set the IO scheduler to NOOP on the SSD

This is what did work:
https://wiki.archlinux.org/index.php/Nv … ries_cards

Last edited by falconindy (2011-01-20 02:30:33)

Arch Linux

#1 2011-01-10 14:06:49

[SOLVED] Short and random CPU spikes only in X

#2 2011-01-10 14:21:51

Re: [SOLVED] Short and random CPU spikes only in X

#3 2011-01-10 14:26:19

Re: [SOLVED] Short and random CPU spikes only in X

#4 2011-01-11 14:16:06

Re: [SOLVED] Short and random CPU spikes only in X

#5 2011-01-11 16:00:53

Re: [SOLVED] Short and random CPU spikes only in X

#6 2011-01-18 04:38:50

Re: [SOLVED] Short and random CPU spikes only in X

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