On Tue, Feb 14, 2017 at 09:32:20AM +0100, Olivier Matz wrote: > Hi Bruce, > > On Tue, 7 Feb 2017 14:12:38 +0000, Bruce Richardson > <bruce.richard...@intel.com> wrote: > > This patchset make a set of, sometimes non-backward compatible, > > cleanup changes to the rte_ring code in order to improve it. The > > resulting code is shorter*, since the existing functions are > > restructured to reduce code duplication, as well as being more > > consistent in behaviour. The specific changes made are explained in > > each patch which makes that change. > > > > Key incompatibilities: > > * The biggest, and probably most controversial change is that to the > > enqueue and dequeue APIs. The enqueue/deq burst and bulk functions > > have their function prototypes changed so that they all return an > > additional parameter, indicating the size of next call which is > > guaranteed to succeed. In case on enq, this is the number of > > available slots on the ring, and in case of deq, it is the number of > > objects which can be pulled. As well as this, the return value from > > the bulk functions have been changed to make them compatible with the > > burst functions. In all cases, the functions to enq/deq a set of objs > > now return the number of objects processed, 0 or N, in the case of > > bulk functions, 0, N or any value in between in the case of the burst > > ones. [Due to the extra parameter, the compiler will flag all > > instances of the function to allow the user to also change the return > > value logic at the same time] > > * The parameters to the single object enq/deq functions have not been > > changed. Because of that, the return value is also unmodified - as > > the compiler cannot automatically flag this to the user. > > > > Potential further cleanups: > > * To a certain extent the rte_ring structure has gone from being a > > whole ring structure, including a "ring" element itself, to just > > being a header which can be reused, along with the head/tail update > > functions to create new rings. For now, the enqueue code works by > > assuming that the ring data goes immediately after the header, but > > that can be changed to allow specialised ring implementations to put > > additional metadata of their own after the ring header. I didn't see > > this as being needed right now, but it may be worth considering for a > > V1 patchset. > > * There are 9 enqueue functions and 9 dequeue functions in > > rte_ring.h. I suspect not all of those are used, so personally I > > would consider dropping the functions to enqueue/dequeue a single > > value using single or multi semantics, i.e. drop > > rte_ring_sp_enqueue > > rte_ring_mp_enqueue > > rte_ring_sc_dequeue > > rte_ring_mc_dequeue > > That would still leave a single enqueue and dequeue function for > > working with a single object at a time. > > * It should be possible to merge the head update code for enqueue and > > dequeue into a single function. The key difference between the two > > is the calculation of how far the index can be moved. I felt that the > > functions for moving the head index are sufficiently complicated > > with many parameters to them already, that trying to merge in more > > code would impede readability. However, if so desired this change can > > be made at a later stage without affecting ABI or API. > > > > PERFORMANCE: > > I've run performance autotests on a couple of (Intel) platforms. > > Looking particularly at the core-2-core results, which I expect are > > the main ones of interest, the performance after this patchset is a > > few cycles per packet faster in my testing. I'm hoping it should be > > at least neutral perf-wise. > > > > REQUEST FOR FEEDBACK: > > * Are all of these changes worth making? > > I've quickly browsed all the patches. I think yes, we should do it: it > brings a good cleanup, removing features we don't need, restructuring > the code, and also adding the feature you need :) > > > > * Should they be made in existing ring code, or do we look to provide > > a new fifo library to completely replace the ring one? > > I think it's ok to have it in the existing code. Breaking the ABI > is never suitable, but I think having 2 libs would be even more > confusing. > > > > * How does the implementation of new ring types using this code > > compare vs that of the previous RFCs? > > I prefer this version, especially compared to the first RFC. > > > Thanks for this big rework. I'll dive into the patches a do a more > exhaustive review soon. > Great, thanks. I'm aware of a few things that already need to be cleaned up for V1 e.g. comments are not always correctly updated on functions.
/Bruce
