On 2018-07-13 08:47 PM, Marek Olšák wrote: > On Fri, Jul 13, 2018 at 4:28 AM, Michel Dänzer <michel at daenzer.net> wrote: >> On 2018-07-12 07:03 PM, Marek Olšák wrote: >>> On Thu, Jul 12, 2018, 3:31 AM Michel Dänzer <michel at daenzer.net> wrote: >>>> >>>> What is the rationale for this? I.e. why do you want to not store some >>>> handles in the hash table? >>> >>> >>> Because I have the option. >> >> Seems like you're expecting this patch to be accepted without providing >> any real justification for it (here or in the corresponding Mesa patch). >> NAK from me if so. > > The real justification is implied by the patch. See: amdgpu_add_handle_to_table > Like I said: There is no risk of regression and it simplifies one > simple case trivially. We shouldn't have to even talk about it. IMO you haven't provided enough justification for adding API which is prone to breakage if used incorrectly. Other opinions? >> I'd rather add the handle to the hash table in amdgpu_bo_alloc, >> amdgpu_create_bo_from_user_mem and amdgpu_bo_import instead of in >> amdgpu_bo_export, making amdgpu_bo_export(bo, amdgpu_bo_handle_type_kms, >> ...) essentially free. In the unlikely (since allocating a BO from the >> kernel is expensive) case that the hash table shows up on profiles, we >> can optimize it. > > The hash table isn't very good for high BO counts. The time complexity > of a lookup is O(n). A lookup is only needed in amdgpu_bo_import. amdgpu_bo_alloc and amdgpu_create_bo_from_user_mem can just add the handle to the hash bucket directly. Do you know of, or can you imagine, any workload where amdgpu_bo_import is called often enough for this to be a concern? -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
