| Message ID | 1489003397-2321-1-git-send-email-sagi@grimberg.me (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
This looks fine in principle, but any performance number showing how this helps (or at least doesn't hurt)? -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 2017-03-08 at 22:03 +0200, Sagi Grimberg wrote: > [ ... ] Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>-- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> This looks fine in principle, but any performance number showing > how this helps (or at least doesn't hurt)? I had it back when I noticed it and came up with this patch, but it was a while ago... Also, IIRC Ming ran it at some point. I'll rerun it though. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 2017-03-08 at 22:03 +0200, Sagi Grimberg wrote: > This workqueue is used by our storage target mode ULPs > via the new CQ API. Recent observations when working > with very high-end flash storage devices reveal that > UNBOUND workqueue threads can migrate between cpu cores > and even numa nodes (although some numa locality is accounted > for). > > While this attribute can be useful in some workloads, > it does not fit in very nicely with the normal > run-to-completion model we usually use in our target-mode > ULPs and the block-mq irq<->cpu affinity facilities. > > The whole block-mq concept is that the completion will > land on the same cpu where the submission was performed. > The fact that our submitter thread is migrating cpus > can break this locality. > > We assume that as a target mode ULP, we will serve multiple > initiators/clients and we can spread the load enough without > having to use unbound kworkers. > > Also, while we're at it, expose this workqueue via sysfs which > is harmless and can be useful for debug. > > Signed-off-by: Sagi Grimberg <sagi@grimberg.me> Thanks, applied.
diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c index 593d2ce6ec7c..fb5ae9564e80 100644 --- a/drivers/infiniband/core/device.c +++ b/drivers/infiniband/core/device.c @@ -1015,8 +1015,7 @@ static int __init ib_core_init(void) return -ENOMEM; ib_comp_wq = alloc_workqueue("ib-comp-wq", - WQ_UNBOUND | WQ_HIGHPRI | WQ_MEM_RECLAIM, - WQ_UNBOUND_MAX_ACTIVE); + WQ_HIGHPRI | WQ_MEM_RECLAIM | WQ_SYSFS, 0); if (!ib_comp_wq) { ret = -ENOMEM; goto err;
This workqueue is used by our storage target mode ULPs via the new CQ API. Recent observations when working with very high-end flash storage devices reveal that UNBOUND workqueue threads can migrate between cpu cores and even numa nodes (although some numa locality is accounted for). While this attribute can be useful in some workloads, it does not fit in very nicely with the normal run-to-completion model we usually use in our target-mode ULPs and the block-mq irq<->cpu affinity facilities. The whole block-mq concept is that the completion will land on the same cpu where the submission was performed. The fact that our submitter thread is migrating cpus can break this locality. We assume that as a target mode ULP, we will serve multiple initiators/clients and we can spread the load enough without having to use unbound kworkers. Also, while we're at it, expose this workqueue via sysfs which is harmless and can be useful for debug. Signed-off-by: Sagi Grimberg <sagi@grimberg.me> --- drivers/infiniband/core/device.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)