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SubjectRe: dlm: Use cmwq for send and receive workqueues
On Fri, Nov 12, 2010 at 12:12:29PM +0000, Steven Whitehouse wrote:
>
> So far as I can tell, there is no reason to use a single-threaded
> send workqueue for dlm, since it may need to send to several sockets
> concurrently. Both workqueues are set to WQ_MEM_RECLAIM to avoid
> any possible deadlocks, WQ_HIGHPRI since locking traffic is highly
> latency sensitive (and to avoid a priority inversion wrt GFS2's
> glock_workqueue) and WQ_FREEZABLE just in case someone needs to do
> that (even though with current cluster infrastructure, it doesn't
> make sense as the node will most likely land up ejected from the
> cluster) in the future.

Thanks, I'll want to do some testing with this, but my test machines do
not seem to create more than one dlm_recv workqueue thread (prior to this
patch). Have you tested in any cases where many threads end up being
created? I've noticed while debugging some many-cpu machines a huge
number of dlm_recv threads, which is just excessive. Does this patch
address that?


> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
> Cc: Tejun Heo <tj@kernel.org>
>
> diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
> index 37a34c2..0893b30 100644
> --- a/fs/dlm/lowcomms.c
> +++ b/fs/dlm/lowcomms.c
> @@ -1431,14 +1431,16 @@ static void work_stop(void)
> static int work_start(void)
> {
> int error;
> - recv_workqueue = create_workqueue("dlm_recv");
> + recv_workqueue = alloc_workqueue("dlm_recv", WQ_MEM_RECLAIM |
> + WQ_HIGHPRI | WQ_FREEZEABLE, 0);
> error = IS_ERR(recv_workqueue);
> if (error) {
> log_print("can't start dlm_recv %d", error);
> return error;
> }
>
> - send_workqueue = create_singlethread_workqueue("dlm_send");
> + send_workqueue = alloc_workqueue("dlm_send", WQ_MEM_RECLAIM |
> + WQ_HIGHPRI | WQ_FREEZEABLE, 0);
> error = IS_ERR(send_workqueue);
> if (error) {
> log_print("can't start dlm_send %d", error);
>
>


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