Heavy disk I/O causes X rendering to hang

Asked by Johannes H. Jensen on 2011-05-30

I get some weird X behavior when my computer is under high I/O load. For some reason, X struggles with rendering (I think), causing long delays in program execution.

Test to reproduce:

1. Start 'stress -d 2' to start hard-drive I/O
2. In another terminal, execute 'time ls /usr/bin'
3. Watch how the ls command hangs for many seconds.

The 'hanging' sometimes occurs before any output appears, other times it hangs in the middle of the output. The worst I've seen is 18 seconds before the command completes. The whole terminal window also hangs at this point.

Now I thought this was related to bug #131094, but I discovered that if I run the same test through SSH, there's no hanging! So the problem seems to be with X rendering the output of the command in the terminal.

I've tested this with the proprietary nvidia driver, the nouveau driver and vesa driver. I got the same problem in all three cases.

System information:
- Ubuntu 11.04 64bit
- NVIDIA GeForce GTS 250

I'm not sure how to debug this further. Please let me know if there's any other information you require.

Question information

Language:
English Edit question
Status:
Open
For:
Ubuntu xserver-xorg-video-nv Edit question
Assignee:
No assignee Edit question
Last query:
2011-05-30
Last reply:
2011-05-30
Sam_ (and-sam) said : #1

Anything meaningful in syslog or kern.log during procedure?
There has been xserver update today, update and see if the issue remains.
http://changelogs.ubuntu.com/changelogs/pool/main/x/xorg-server/xorg-server_1.10.1-1ubuntu1/changelog

There is also an xorg-egders ppa for testing purpose.
https://launchpad.net/~xorg-edgers/+archive/ppa

I'd also try a websearch with graphic card+xserver.

Johannes H. Jensen (joh) said : #2

Hi,

On Mon, May 30, 2011 at 3:50 PM, Sam_
<email address hidden> wrote:
> Anything meaningful in syslog or kern.log during procedure?

No, nothing in the logs I'm afraid...

> There has been xserver update today, update and see if the issue remains.
> http://changelogs.ubuntu.com/changelogs/pool/main/x/xorg-server/xorg-server_1.10.1-1ubuntu1/changelog

Just updated and the issue very much remains.

> There is also an xorg-egders ppa for testing purpose.
> https://launchpad.net/~xorg-edgers/+archive/ppa

I'll try the xorg-edgers packages later today and report back.

> I'd also try a websearch with graphic card+xserver.

Searched around quite a bit, but haven't found anything related...

- Johannes

Sam_ (and-sam) said : #3

No idea where my comment went, so retry.
Which session, Unity, Classic (Gnome), Compiz or no effects?
Maybe a backup is running in background and takes lots of CPU?
I'd create a test-user to see if the issue remains.
Only found Bug #771788 about drivers not activated.

https://wiki.ubuntu.com/X/Troubleshooting/

Johannes H. Jensen (joh) said : #4

Tested both with Unity and Classic (no effects). There are no other background processes consuming CPU resources when testing (verified with system monitor). I'll try creating a test user.

Johannes H. Jensen (joh) said : #5

Same problem with a newly created test user. I'll try xorg-edgers next.

Johannes H. Jensen (joh) said : #6

I just tested with the packages from xorg-edgers (added the ppa, update and dist-upgrade).

The problem is still very much there.

Should I file a bug at this point?

Sam_ (and-sam) said : #7

Yep, I'd say since it's very much reproducable it should be ok to report one and give experts a chance to advise how to get to the ground of the issue.
https://help.ubuntu.com/community/ReportingBugs

Could be graphic driver, xorg leaking or else.

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