On 5/15/20 8:34 AM, Stefano Garzarella wrote: > On Fri, May 15, 2020 at 08:24:58AM -0600, Jens Axboe wrote: >> On 5/15/20 4:54 AM, Stefano Garzarella wrote: >>> The first patch adds the new 'cq_flags' field for the CQ ring. It >>> should be written by the application and read by the kernel. >>> >>> The second patch adds a new IORING_CQ_NEED_WAKEUP flag that can be >>> used by the application to enable/disable eventfd notifications. >>> >>> I'm not sure the name is the best one, an alternative could be >>> IORING_CQ_NEED_EVENT. >>> >>> This feature can be useful if the application are using eventfd to be >>> notified when requests are completed, but they don't want a notification >>> for every request. >>> Of course the application can already remove the eventfd from the event >>> loop, but as soon as it adds the eventfd again, it will be notified, >>> even if it has already handled all the completed requests. >>> >>> The most important use case is when the registered eventfd is used to >>> notify a KVM guest through irqfd and we want a mechanism to >>> enable/disable interrupts. >>> >>> I also extended liburing API and added a test case here: >>> https://github.com/stefano-garzarella/liburing/tree/eventfd-disable >> >> Don't mind the feature, and I think the patches look fine. But the name >> is really horrible, I'd have no idea what that flag does without looking >> at the code or a man page. Why not call it IORING_CQ_EVENTFD_ENABLED or >> something like that? Or maybe IORING_CQ_EVENTFD_DISABLED, and then you >> don't have to muck with the default value either. The app would set the >> flag to disable eventfd, temporarily, and clear it again when it wants >> notifications again. > > You're clearly right! :-) The name was horrible. Sometimes you go down that path on naming and just can't think of the right one. I think we've all been there. > I agree that IORING_CQ_EVENTFD_DISABLED should be the best. > I'll send a v2 changing the name and removing the default value. Great thanks, and please do queue a pull for the liburing side too. -- Jens Axboe
