> > > > > Added cache guard after the table holding the ring elements, to > > avoid > > > > > false sharing conflicts caused by next-line hardware prefetchers > > when > > > > > accessing elements at the end of the ring table. > > > > > > > > I don't see any harm with it, and in theory it might help in some > > > > cases... > > > > Though I wonder how real is that problem? > > > > Did you ever observe such contention to happen? > > > > > > I never observed a problem with this. > > > The risk of contention depends on what is allocated in the memory > > after the ring. > > > Which is application specific. > > > > > > It seems like a purely theoretical issue, but should be fixed anyway, > > to eliminate > > > that risk. > > > > Ok, as I said I see no harm with it. > > Should we document this change somewhere? RN or PG? > > We don't want the release notes overflowing with minor details. > IMO, this change is below the threshold for what people might care about. > People interested in the detailed changes between releases should read the git > log.
I still think we do need document somewhere why we doing it. If you think RN or PG is not the right place, let's just put it as a comment for that particular function. > Also, I don't think it's worth backporting, because I consider it unlikely to > have > any real effect. > In the context of backporting, it could be considered a performance > improvement rather than a bug fix. I don't see much point to backport it. > > > Acked-by: Konstantin Ananyev <[email protected]> > > > > > > > > > > > Signed-off-by: Morten Brørup <[email protected]> > > > > > --- > > > > > lib/ring/rte_ring.c | 3 +++ > > > > > 1 file changed, 3 insertions(+) > > > > > > > > > > diff --git a/lib/ring/rte_ring.c b/lib/ring/rte_ring.c > > > > > index f10050a1c4..9ccc62cd42 100644 > > > > > --- a/lib/ring/rte_ring.c > > > > > +++ b/lib/ring/rte_ring.c > > > > > @@ -73,8 +73,11 @@ rte_ring_get_memsize_elem(unsigned int esize, > > > > unsigned > > > > > int count) > > > > > return -EINVAL; > > > > > } > > > > > > > > > > + static_assert(sizeof(struct rte_ring) == > > > > > RTE_CACHE_LINE_ROUNDUP(sizeof(struct rte_ring)), > > > > > + "Size of struct rte_ring not cache line > > aligned"); > > > > > sz = sizeof(struct rte_ring) + (ssize_t)count * esize; > > > > > sz = RTE_ALIGN(sz, RTE_CACHE_LINE_SIZE); > > > > > + sz += RTE_CACHE_GUARD_LINES * RTE_CACHE_LINE_SIZE; > > > > > return sz; > > > > > } > > > > > > > > > > -- > > > > > 2.43.0
