On 12/19/2016 11:21 AM, Paolo Valente wrote: > >> Il giorno 19 dic 2016, alle ore 16:20, Jens Axboe <ax...@fb.com> ha scritto: >> >> On 12/19/2016 04:32 AM, Paolo Valente wrote: >>> >>>> Il giorno 17 dic 2016, alle ore 01:12, Jens Axboe <ax...@fb.com> ha >>>> scritto: >>>> >>>> This is version 4 of this patchset, version 3 was posted here: >>>> >>>> https://marc.info/?l=linux-block&m=148178513407631&w=2 >>>> >>>> From the discussion last time, I looked into the feasibility of having >>>> two sets of tags for the same request pool, to avoid having to copy >>>> some of the request fields at dispatch and completion time. To do that, >>>> we'd have to replace the driver tag map(s) with our own, and augment >>>> that with tag map(s) on the side representing the device queue depth. >>>> Queuing IO with the scheduler would allocate from the new map, and >>>> dispatching would acquire the "real" tag. We would need to change >>>> drivers to do this, or add an extra indirection table to map a real >>>> tag to the scheduler tag. We would also need a 1:1 mapping between >>>> scheduler and hardware tag pools, or additional info to track it. >>>> Unless someone can convince me otherwise, I think the current approach >>>> is cleaner. >>>> >>>> I wasn't going to post v4 so soon, but I discovered a bug that led >>>> to drastically decreased merging. Especially on rotating storage, >>>> this release should be fast, and on par with the merging that we >>>> get through the legacy schedulers. >>>> >>> >>> I'm to modifying bfq. You mentioned other missing pieces to come. Do >>> you already have an idea of what they are, so that I am somehow >>> prepared to what won't work even if my changes are right? >> >> I'm mostly talking about elevator ops hooks that aren't there in the new >> framework, but exist in the old one. There should be no hidden >> surprises, if that's what you are worried about. >> >> On the ops side, the only ones I can think of are the activate and >> deactivate, and those can be done in the dispatch_request hook for >> activate, and put/requeue for deactivate. >> > > You mean that there is no conceptual problem in moving the code of the > activate interface function into the dispatch function, and the code > of the deactivate into the put_request? (for a requeue it is a little > less clear to me, so one step at a time) Or am I missing > something more complex?
Yes, what I mean is that there isn't a 1:1 mapping between the old ops and the new ops. So you'll have to consider the cases. -- Jens Axboe
