From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: Re: [RFC workqueue/driver-core PATCH 1/5] workqueue: Provide queue_work_near to queue work near a given NUMA node Date: Mon, 1 Oct 2018 14:54:39 -0700 Message-ID: <4eebc017-23a2-a26e-095c-66433061a141@linux.intel.com> References: <20180926214433.13512.30289.stgit@localhost.localdomain> <20180926215138.13512.33146.stgit@localhost.localdomain> <20180926215307.GA270328@devbig004.ftw2.facebook.com> <9b002bbb-3e6d-9e99-d8f9-36df4306093e@linux.intel.com> <20180926220957.GB270328@devbig004.ftw2.facebook.com> <20181001160142.GE270328@devbig004.ftw2.facebook.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20181001160142.GE270328-LpCCV3molIbIZ9tKgghJQw2O0Ztt9esIQQ4Iyu8u01E@public.gmane.org> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: Tejun Heo Cc: len.brown-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org, jiangshanlai-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, zwisler-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, pavel-+ZI9xUNit7I@public.gmane.org, rafael-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org List-Id: linux-pm@vger.kernel.org On 10/1/2018 9:01 AM, Tejun Heo wrote: > Hello, > > On Wed, Sep 26, 2018 at 03:19:21PM -0700, Alexander Duyck wrote: >> On 9/26/2018 3:09 PM, Tejun Heo wrote: >> I could just use queue_work_on probably, but is there any issue if I >> am passing CPU values that are not in the wq_unbound_cpumask? That > > That should be fine. If it can't find any available cpu, it'll fall > back to round-robin. We probably can improve it so that it can > consider the numa distance when falling back. > >> was mostly my concern. Also for an unbound queue do I need to worry >> about the hotplug lock? I wasn't sure if that was the case or not as > > Issuers don't need to worry about them. > >> I know it is called out as something to be concerned with using >> queue_work_on, but in __queue_work the value is just used to >> determine which node to grab a work queue from. > > It might be better to leave queue_work_on() to be used for per-cpu > workqueues and introduce queue_work_near() as you suggseted. I just > don't want it to duplicate the node selection code in it. Would that > work? So if I understand what you are saying correctly we default to round-robin on a given node has no CPUs attached to it. I could probably work with that if that is the default behavior instead of adding much of the complexity I already have. The question I have then is what should I do about workqueues that aren't WQ_UNBOUND if they attempt to use queue_work_near? In that case I should be looking for some way to go from a node to a CPU shouldn't I? If so should I look at doing something like wq_select_unbound_cpu that uses the node cpumask instead of the wq_unbound_cpumask? - Alex