Hello, On Thu, Feb 24, 2011 at 09:23:03AM -0500, Vivek Goyal wrote:
On Thu, Feb 24, 2011 at 10:18:00AM +0100, Dominik Klein wrote:
Hi Dominik,
Thanks for the tests and reports. I checked the latest logs also and I see that cfq has scheduled a work but that work never gets scheduled. I never see the trace message which says cfq_kick_queue().
I am ccing it to lkml and tejun to see if he has any suggestions.
Tejun,
I will give you some details about what we have discussed so far.
Dominik is trying blkio throttling feature and trying to throttle some virtual machines. He is using 2.6.37 kernels and once he launches 3 virtual machines he notices that system is kind of frozen. After running some traces we noticed that CFQ has requests but it is not dispatching these to devices any more.
This problem does not show up with deadline scheduler and also goes away with 2.6.38-rc6 kernels.
Hmmm... Maybe the following commit? commit 7576958a9d5a4a677ad7dd40901cdbb6c1110c98 Author: Tejun Heo <tj@kernel.org> Date: Mon Feb 14 14:04:46 2011 +0100 workqueue: wake up a worker when a rescuer is leaving a gcwq After executing the matching works, a rescuer leaves the gcwq whether there are more pending works or not. This may decrease the concurrency level to zero and stall execution until a new work item is queued on the gcwq. Make rescuer wake up a regular worker when it leaves a gcwq if there are more works to execute, so that execution isn't stalled. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Ray Jui <rjui@broadcom.com> Cc: stable@kernel.org -- tejun