> From: Andrzej Ostruszka [mailto:a...@semihalf.com] > Sent: Tuesday, 11 January 2022 12.38 > > When enqueueing/dequeueing to/from the ring we try to optimize by > manual > loop unrolling. The check for this optimization looks like: > > if (likely(idx + n < size)) { > > where 'idx' points to the first usable element (empty slot for enqueue, > data for dequeue). The correct comparison here should be '<=' instead > of '<'. > > This is not a functional error since we fall back to the loop with > correct checks on indexes. Just a minor suboptimal behaviour for the > case when we want to enqueue/dequeue exactly the number of elements > that > we have in the ring before wrapping to its beginning. > > Fixes: cc4b218790f6 ("ring: support configurable element size") > Fixes: 286bd05bf70d ("ring: optimisations") > > Signed-off-by: Andrzej Ostruszka <a...@semihalf.com> > Reviewed-by: Olivier Matz <olivier.m...@6wind.com> > Acked-by: Konstantin Ananyev <konstantin.anan...@intel.com> > --- > lib/ring/rte_ring_elem_pvt.h | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/lib/ring/rte_ring_elem_pvt.h > b/lib/ring/rte_ring_elem_pvt.h > index 275ec55393..83788c56e6 100644 > --- a/lib/ring/rte_ring_elem_pvt.h > +++ b/lib/ring/rte_ring_elem_pvt.h > @@ -17,7 +17,7 @@ __rte_ring_enqueue_elems_32(struct rte_ring *r, const > uint32_t size, > unsigned int i; > uint32_t *ring = (uint32_t *)&r[1]; > const uint32_t *obj = (const uint32_t *)obj_table; > - if (likely(idx + n < size)) { > + if (likely(idx + n <= size)) { > for (i = 0; i < (n & ~0x7); i += 8, idx += 8) { > ring[idx] = obj[i]; > ring[idx + 1] = obj[i + 1]; > @@ -62,7 +62,7 @@ __rte_ring_enqueue_elems_64(struct rte_ring *r, > uint32_t prod_head, > uint32_t idx = prod_head & r->mask; > uint64_t *ring = (uint64_t *)&r[1]; > const unaligned_uint64_t *obj = (const unaligned_uint64_t > *)obj_table; > - if (likely(idx + n < size)) { > + if (likely(idx + n <= size)) { > for (i = 0; i < (n & ~0x3); i += 4, idx += 4) { > ring[idx] = obj[i]; > ring[idx + 1] = obj[i + 1]; > @@ -95,7 +95,7 @@ __rte_ring_enqueue_elems_128(struct rte_ring *r, > uint32_t prod_head, > uint32_t idx = prod_head & r->mask; > rte_int128_t *ring = (rte_int128_t *)&r[1]; > const rte_int128_t *obj = (const rte_int128_t *)obj_table; > - if (likely(idx + n < size)) { > + if (likely(idx + n <= size)) { > for (i = 0; i < (n & ~0x1); i += 2, idx += 2) > memcpy((void *)(ring + idx), > (const void *)(obj + i), 32); > @@ -151,7 +151,7 @@ __rte_ring_dequeue_elems_32(struct rte_ring *r, > const uint32_t size, > unsigned int i; > uint32_t *ring = (uint32_t *)&r[1]; > uint32_t *obj = (uint32_t *)obj_table; > - if (likely(idx + n < size)) { > + if (likely(idx + n <= size)) { > for (i = 0; i < (n & ~0x7); i += 8, idx += 8) { > obj[i] = ring[idx]; > obj[i + 1] = ring[idx + 1]; > @@ -196,7 +196,7 @@ __rte_ring_dequeue_elems_64(struct rte_ring *r, > uint32_t prod_head, > uint32_t idx = prod_head & r->mask; > uint64_t *ring = (uint64_t *)&r[1]; > unaligned_uint64_t *obj = (unaligned_uint64_t *)obj_table; > - if (likely(idx + n < size)) { > + if (likely(idx + n <= size)) { > for (i = 0; i < (n & ~0x3); i += 4, idx += 4) { > obj[i] = ring[idx]; > obj[i + 1] = ring[idx + 1]; > @@ -229,7 +229,7 @@ __rte_ring_dequeue_elems_128(struct rte_ring *r, > uint32_t prod_head, > uint32_t idx = prod_head & r->mask; > rte_int128_t *ring = (rte_int128_t *)&r[1]; > rte_int128_t *obj = (rte_int128_t *)obj_table; > - if (likely(idx + n < size)) { > + if (likely(idx + n <= size)) { > for (i = 0; i < (n & ~0x1); i += 2, idx += 2) > memcpy((void *)(obj + i), (void *)(ring + idx), 32); > switch (n & 0x1) { > -- > 2.34.1.575.g55b058a8bb-goog >
Also this version of the patch: Reviewed-by: Morten Brørup <m...@smartsharesystems.com>
