[PATCH io_uring for-6.18 01/20] io_uring/zcrx: improve rqe cache alignment
From: Pavel Begunkov <asml.silence@gmail.com>
Date: 2025-09-16 14:26:48
Also in:
io-uring
Subsystem:
io_uring, io_uring zcrx, the rest · Maintainers:
Jens Axboe, Pavel Begunkov, Linus Torvalds
Refill queue entries are 16B structures, but because of the ring header placement, they're 8B aligned but not naturally / 16B aligned, which means some of them span across 2 cache lines. Push rqes to a new cache line. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> --- io_uring/zcrx.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 51fd2350dbe9..c02045e4c1b6 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c@@ -352,7 +352,7 @@ static int io_allocate_rbuf_ring(struct io_zcrx_ifq *ifq, void *ptr; int ret; - off = sizeof(struct io_uring); + off = ALIGN(sizeof(struct io_uring), L1_CACHE_BYTES); size = off + sizeof(struct io_uring_zcrx_rqe) * reg->rq_entries; if (size > rd->size) return -EINVAL;
@@ -367,6 +367,10 @@ static int io_allocate_rbuf_ring(struct io_zcrx_ifq *ifq, ptr = io_region_get_ptr(&ifq->region); ifq->rq_ring = (struct io_uring *)ptr; ifq->rqes = (struct io_uring_zcrx_rqe *)(ptr + off); + + reg->offsets.head = offsetof(struct io_uring, head); + reg->offsets.tail = offsetof(struct io_uring, tail); + reg->offsets.rqes = off; return 0; }
@@ -618,9 +622,6 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx, goto err; ifq->if_rxq = reg.if_rxq; - reg.offsets.rqes = sizeof(struct io_uring); - reg.offsets.head = offsetof(struct io_uring, head); - reg.offsets.tail = offsetof(struct io_uring, tail); reg.zcrx_id = id; scoped_guard(mutex, &ctx->mmap_lock) {
--
2.49.0