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. Regards, Olivier
