Re: [libvirt] Is it a workqueue related issue in 2.6.37 (Was: Re: blkio cgroup [solved])
On Fri, Feb 25, 2011 at 08:24:15AM +0100, Dominik Klein wrote:
> Maybe watching what the workqueue is doing using the following
trace
> events could be helpful.
>
> # grep workqueue /sys/kernel/debug/tracing/available_events
> workqueue:workqueue_insertion
> workqueue:workqueue_execution
> workqueue:workqueue_creation
> workqueue:workqueue_destruction
Since I've never done this before, I will tell you how I captured the
trace so you know what I did and can see whether I did something wrong
and can correct me if necessary.
echo blk > /sys/kernel/debug/tracing/current_tracer
echo 1 > /sys/block/sdb/trace/enable
echo workqueue_queue_work >> /sys/kernel/debug/tracing/set_event
echo workqueue_activate_work >> /sys/kernel/debug/tracing/set_event
echo workqueue_execute_start >> /sys/kernel/debug/tracing/set_event
echo workqueue_execute_end >> /sys/kernel/debug/tracing/set_event
cat /sys/kernel/debug/tracing/trace_pipe
And that output i gzip'd.
This was taken with 2.6.37 plus the patch you mentioned on a Dell R815
with 2 12 core AMD Opteron 6174 CPUs. If you need any more information,
please let me know.
Hmmm... well, I have no idea what you were trying to do but here are
some info which might be helpful.
* queue_work happens when the work item is queued.
* activate_work happens when the work item becomes eligible for
execution. e.g. If the workqueue's @max_active is limited and
maximum number of work items are already in flight, a new item will
only get activated after one of the in flight ones retires.
* execute_start marks the actual starting of execution.
* execute_end marks the end of execution.
So, I would look for the matching work function and then try to follow
what happens to it after being scheduled and if it doesn't get
executed what's going on with the target workqueue.
Thanks.
--
tejun