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5247c034a6
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>