From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Steve Wise" Subject: RE: Flush warning Date: Wed, 9 Aug 2017 11:21:38 -0500 Message-ID: <00ff01d3112b$94142350$bc3c69f0$@opengridcomputing.com> References: <016301d30c86$e7034ae0$b509e0a0$@opengridcomputing.com> <9bc142de-b8ba-acb6-5ea1-2ccdbb578655@grimberg.me> <003401d30f91$c7e2a3f0$57a7ebd0$@opengridcomputing.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <003401d30f91$c7e2a3f0$57a7ebd0$@opengridcomputing.com> Content-Language: en-us Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: 'Sean Hefty' Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, 'Sagi Grimberg' , 'Christoph Hellwig' List-Id: linux-rdma@vger.kernel.org > > > > The WARNING seems to be due to nvmet_rdma_queue_connect() calling > > > flush_scheduled_work() while in the upcall from the RDMA_CM. It I running > on > > > the iw_cm event workqueue, which is created with WQ_MEM_RECLAIM set. > I'm > > not > > > sure what this WARNING is telling me. Does the iw_cm workqueue NOT need > > > WQ_MEM_RECLAIM set? Or is there some other issue with the nvmet/rdma > > code doing > > > work flushing in the iw_cm workq context? > > > > This flush is designed to prevent nvmet-rdma from having too much > > inflight resources in case of a high pace of controller teardown and > > establishment (like you trigger in your test). > > > > queue teardowns are run on system_wq, does iw_cm needs memory > > reclamation protection? > > I don't know. I read the workqueue doc on WQ_MEM_RECLAIM, but I don't know > how > to tell if iw_cm needs this or not. Can you give me an example of a workqueue > that _does_ need WQ_MEM_RECLAIM? I _think_ it means your workqueue is > required > to run something that would get triggered by the oom OS code, but I don't know > if that would include rdma CMs or not... Many of the workqueues in infiniband/core use WQ_MEM_RECLAIM: cma, iwcm, mad, multicast, sa_query, and ucma. Hey Sean, do you have any insight into whether the CMA modules really need WQ_MEM_RECLAIM for their workqueues? Does anyone else know? Thanks! Steve. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html