On 9/10/20 1:03 AM, Xiaoguang Wang wrote: > We have already supported multiple rings to share one same poll thread > by passing IORING_SETUP_ATTACH_WQ, but it's not that convenient to use. > IORING_SETUP_ATTACH_WQ needs users to ensure that a parent ring instance > has already existed, that means it will require app to regulate the > creation oder between uring instances. > > Currently we can make this a bit simpler, for those rings which will > have SQPOLL enabled and are willing to be bound to one same cpu, add a > capability that these rings can share one poll thread by specifying > a new IORING_SETUP_SQPOLL_PERCPU flag, then we have 3 cases > 1, IORING_SETUP_ATTACH_WQ: if user specifies this flag, we'll always > try to attach this ring to an existing ring's corresponding poll thread, > no matter whether IORING_SETUP_SQ_AFF or IORING_SETUP_SQPOLL_PERCPU is > set. > 2, IORING_SETUP_SQ_AFF and IORING_SETUP_SQPOLL_PERCPU are both enabled, > for this case, we'll create a single poll thread to be shared by these > rings, and this poll thread is bound to a fixed cpu. > 3, for any other cases, we'll just create one new poll thread for the > corresponding ring. > > And for case 2, don't need to regulate creation oder of multiple uring > instances, we use a mutex to synchronize creation, for example, say five > rings which all have IORING_SETUP_SQ_AFF & IORING_SETUP_SQPOLL_PERCPU > enabled, and are willing to be bound same cpu, one ring that gets the > mutex lock will create one poll thread, the other four rings will just > attach themselves the previous created poll thread. > > To implement above function, add one global hlist_head hash table, only > sqd that is created for IORING_SETUP_SQ_AFF & IORING_SETUP_SQPOLL_PERCPU > will be added to this global list, and its search key are current->files > and cpu number. Can you resend this against the current tree? Looks like it's against something that is outdated. That'll make it easier to test and review. -- Jens Axboe
