> From: netdev-ow...@vger.kernel.org [mailto:netdev-ow...@vger.kernel.org] On > Behalf Of Yunsheng Lin > Sent: Tuesday, May 28, 2019 2:04 AM > > On 2019/5/27 22:58, Stephen Hemminger wrote: > > On Mon, 27 May 2019 09:47:54 +0800 > > Yunsheng Lin <linyunsh...@huawei.com> wrote: > > > >> When user has configured a large number of virtual netdev, such > >> as 4K vlans, the carrier on/off operation of the real netdev > >> will also cause it's virtual netdev's link state to be processed > >> in linkwatch. Currently, the processing is done in a work queue, > >> which may cause worker starvation problem for other work queue.
I think we had already discussed about this internally and using separate workqueue with WQ_UNBOUND should solve this problem. HNS3 driver was sharing workqueue with the system workqueue. > >> This patch releases the cpu when link watch worker has processed > >> a fixed number of netdev' link watch event, and schedule the > >> work queue again when there is still link watch event remaining. We need proper examples/use-cases because of which we require above kind of co-operative scheduling. Touching the common shared queue logic which solid argument might invite for more problem to other modules. > >> Signed-off-by: Yunsheng Lin <linyunsh...@huawei.com> > > > > Why not put link watch in its own workqueue so it is scheduled > > separately from the system workqueue? > > From testing and debuging, the workqueue runs on the cpu where the > workqueue is schedule when using normal workqueue, even using its > own workqueue instead of system workqueue. So if the cpu is busy > processing the linkwatch event, it is not able to process other > workqueue' work when the workqueue is scheduled on the same cpu. > > Using unbound workqueue may solve the cpu starvation problem. [...] > But the __linkwatch_run_queue is called with rtnl_lock, so if it > takes a lot time to process, other need to take the rtnl_lock may > not be able to move forward. Please help me in understanding, Are you trying to pitch this patch to solve more general system issue OR still your argument/concern is related to the HNS3 driver problem mentioned in this patch? Salil.
