diff options
| author | Pavel Begunkov <asml.silence@gmail.com> | 2026-01-20 20:47:40 +0000 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2026-01-22 15:47:23 -0700 |
| commit | 5247c034a67f5a93cc1faa15e9867eec5b22f38a (patch) | |
| tree | dafc8859ac3cc7eaa08dfe3641ba1c8818267717 /include | |
| parent | 0105b0562a5ed6374f06e5cd4246a3f1311a65a0 (diff) | |
io_uring: introduce non-circular SQ
Outside of SQPOLL, normally SQ entries are consumed by the time the
submission syscall returns. For those cases we don't need a circular
buffer and the head/tail tracking, instead the kernel can assume that
entries always start from the beginning of the SQ at index 0. This patch
introduces a setup flag doing exactly that. It's a simpler and helps
to keeps SQEs hot in cache.
The feature is optional and enabled by setting IORING_SETUP_SQ_REWIND.
The flag is rejected if passed together with SQPOLL as it'd require
waiting for SQ before each submission. It also requires
IORING_SETUP_NO_SQARRAY, which can be supported but it's unlikely there
will be users, so leave more space for future optimisations.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/io_uring.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index b5b23c0d5283..475094c7a668 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -237,6 +237,18 @@ enum io_uring_sqe_flags_bit { */ #define IORING_SETUP_SQE_MIXED (1U << 19) +/* + * When set, io_uring ignores SQ head and tail and fetches SQEs to submit + * starting from index 0 instead from the index stored in the head pointer. + * IOW, the user should place all SQE at the beginning of the SQ memory + * before issuing a submission syscall. + * + * It requires IORING_SETUP_NO_SQARRAY and is incompatible with + * IORING_SETUP_SQPOLL. The user must also never change the SQ head and tail + * values and keep it set to 0. Any other value is undefined behaviour. + */ +#define IORING_SETUP_SQ_REWIND (1U << 20) + enum io_uring_op { IORING_OP_NOP, IORING_OP_READV, |