On Thu, Jun 02, 2022 at 08:42:13AM +0300, Lionel Landwerlin wrote: > On 02/06/2022 00:18, Matthew Brost wrote: > > On Wed, Jun 01, 2022 at 05:25:49PM +0300, Lionel Landwerlin wrote: > > > On 17/05/2022 21:32, Niranjana Vishwanathapura wrote: > > > > +VM_BIND/UNBIND ioctl will immediately start binding/unbinding the mapping in an > > > > +async worker. The binding and unbinding will work like a special GPU engine. > > > > +The binding and unbinding operations are serialized and will wait on specified > > > > +input fences before the operation and will signal the output fences upon the > > > > +completion of the operation. Due to serialization, completion of an operation > > > > +will also indicate that all previous operations are also complete. > > > I guess we should avoid saying "will immediately start binding/unbinding" if > > > there are fences involved. > > > > > > And the fact that it's happening in an async worker seem to imply it's not > > > immediate. > > > > > > > > > I have a question on the behavior of the bind operation when no input fence > > > is provided. Let say I do : > > > > > > VM_BIND (out_fence=fence1) > > > > > > VM_BIND (out_fence=fence2) > > > > > > VM_BIND (out_fence=fence3) > > > > > > > > > In what order are the fences going to be signaled? > > > > > > In the order of VM_BIND ioctls? Or out of order? > > > > > > Because you wrote "serialized I assume it's : in order > > > > > > > > > One thing I didn't realize is that because we only get one "VM_BIND" engine, > > > there is a disconnect from the Vulkan specification. > > > > > > In Vulkan VM_BIND operations are serialized but per engine. > > > > > > So you could have something like this : > > > > > > VM_BIND (engine=rcs0, in_fence=fence1, out_fence=fence2) > > > > > > VM_BIND (engine=ccs0, in_fence=fence3, out_fence=fence4) > > > > > Question - let's say this done after the above operations: > > > > EXEC (engine=ccs0, in_fence=NULL, out_fence=NULL) > > > > Is the exec ordered with respected to bind (i.e. would fence3 & 4 be > > signaled before the exec starts)? > > > > Matt > > > Hi Matt, > > From the vulkan point of view, everything is serialized within an engine (we > map that to a VkQueue). > > So with : > > EXEC (engine=ccs0, in_fence=NULL, out_fence=NULL) > VM_BIND (engine=ccs0, in_fence=fence3, out_fence=fence4) > > EXEC completes first then VM_BIND executes. > > > To be even clearer : > > EXEC (engine=ccs0, in_fence=fence2, out_fence=NULL) > VM_BIND (engine=ccs0, in_fence=fence3, out_fence=fence4) > > > EXEC will wait until fence2 is signaled. > Once fence2 is signaled, EXEC proceeds, finishes and only after it is done, VM_BIND executes. > > It would kind of like having the VM_BIND operation be another batch executed from the ringbuffer buffer. > Yea this makes sense. I think of VM_BINDs as more or less just another version of an EXEC and this fits with that. In practice I don't think we can share a ring but we should be able to present an engine (again likely a gem context in i915) to the user that orders VM_BINDs / EXECs if that is what Vulkan expects, at least I think. Hopefully Niranjana + Daniel agree. Matt > -Lionel > > > > > > > fence1 is not signaled > > > > > > fence3 is signaled > > > > > > So the second VM_BIND will proceed before the first VM_BIND. > > > > > > > > > I guess we can deal with that scenario in userspace by doing the wait > > > ourselves in one thread per engines. > > > > > > But then it makes the VM_BIND input fences useless. > > > > > > > > > Daniel : what do you think? Should be rework this or just deal with wait > > > fences in userspace? > > > > > > > > > Sorry I noticed this late. > > > > > > > > > -Lionel > > > > > > >
