Currently any dependent link is executed from a new workqueue context, which means that we'll be doing a context switch per link in the chain. If we are running the completion of the current request from our async workqueue and find that the next request is a link, then run it directly from the workqueue context instead of forcing another switch.
This improves the performance of linked SQEs, and reduces the CPU overhead. Signed-off-by: Jens Axboe <[email protected]> --- v2: - Improve naming - Improve async detection - Harden cases where we could miss req return - Add support for fsync/sync_file_range/recvmsg/sendmsg 2-3x speedup doing read-write links, where the read often ends up blocking. Tested with examples/link-cp.c diff --git a/fs/io_uring.c b/fs/io_uring.c index aa8ac557493c..742d95563a54 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -667,7 +667,7 @@ static void __io_free_req(struct io_kiocb *req) kmem_cache_free(req_cachep, req); } -static void io_req_link_next(struct io_kiocb *req) +struct io_kiocb *io_req_link_next(struct io_kiocb *req) { struct io_kiocb *nxt; @@ -686,9 +686,19 @@ static void io_req_link_next(struct io_kiocb *req) } nxt->flags |= REQ_F_LINK_DONE; + /* + * If we're in async work, we can continue processing this, + * we can continue processing the chain in this context instead + * of having to queue up new async work. + */ + if (current_work()) + return nxt; INIT_WORK(&nxt->work, io_sq_wq_submit_work); io_queue_async_work(req->ctx, nxt); + nxt = NULL; } + + return nxt; } /* @@ -707,8 +717,10 @@ static void io_fail_links(struct io_kiocb *req) } } -static void io_free_req(struct io_kiocb *req) +static struct io_kiocb *io_free_req(struct io_kiocb *req) { + struct io_kiocb *nxt = NULL; + /* * If LINK is set, we have dependent requests in this chain. If we * didn't fail this request, queue the first one up, moving any other @@ -719,16 +731,30 @@ static void io_free_req(struct io_kiocb *req) if (req->flags & REQ_F_FAIL_LINK) io_fail_links(req); else - io_req_link_next(req); + nxt = io_req_link_next(req); } __io_free_req(req); + return nxt; } -static void io_put_req(struct io_kiocb *req) +static struct io_kiocb *__io_put_req(struct io_kiocb *req) { if (refcount_dec_and_test(&req->refs)) - io_free_req(req); + return io_free_req(req); + + return NULL; +} + +static void io_put_req(struct io_kiocb *req) +{ + struct io_kiocb *nxt; + + nxt = __io_put_req(req); + if (nxt) { + INIT_WORK(&nxt->work, io_sq_wq_submit_work); + io_queue_async_work(nxt->ctx, nxt); + } } static unsigned io_cqring_events(struct io_rings *rings) @@ -934,7 +960,7 @@ static void kiocb_end_write(struct kiocb *kiocb) } } -static void io_complete_rw(struct kiocb *kiocb, long res, long res2) +static void io_complete_rw_common(struct kiocb *kiocb, long res) { struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw); @@ -943,9 +969,24 @@ static void io_complete_rw(struct kiocb *kiocb, long res, long res2) if ((req->flags & REQ_F_LINK) && res != req->result) req->flags |= REQ_F_FAIL_LINK; io_cqring_add_event(req->ctx, req->user_data, res); +} + +static void io_complete_rw(struct kiocb *kiocb, long res, long res2) +{ + struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw); + + io_complete_rw_common(kiocb, res); io_put_req(req); } +static struct io_kiocb *__io_complete_rw(struct kiocb *kiocb, long res) +{ + struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw); + + io_complete_rw_common(kiocb, res); + return __io_put_req(req); +} + static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2) { struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw); @@ -1128,6 +1169,15 @@ static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret) } } +static void call_io_rw_done(struct kiocb *kiocb, ssize_t ret, + struct io_kiocb **nxt, bool in_async) +{ + if (in_async && ret >= 0 && nxt && kiocb->ki_complete == io_complete_rw) + *nxt = __io_complete_rw(kiocb, ret); + else + io_rw_done(kiocb, ret); +} + static int io_import_fixed(struct io_ring_ctx *ctx, int rw, const struct io_uring_sqe *sqe, struct iov_iter *iter) @@ -1344,7 +1394,7 @@ static ssize_t loop_rw_iter(int rw, struct file *file, struct kiocb *kiocb, } static int io_read(struct io_kiocb *req, const struct sqe_submit *s, - bool force_nonblock) + bool force_nonblock, struct io_kiocb **nxt) { struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; struct kiocb *kiocb = &req->rw; @@ -1391,7 +1441,7 @@ static int io_read(struct io_kiocb *req, const struct sqe_submit *s, ret2 = -EAGAIN; /* Catch -EAGAIN return for forced non-blocking submission */ if (!force_nonblock || ret2 != -EAGAIN) { - io_rw_done(kiocb, ret2); + call_io_rw_done(kiocb, ret2, nxt, s->needs_lock); } else { /* * If ->needs_lock is true, we're already in async @@ -1407,7 +1457,7 @@ static int io_read(struct io_kiocb *req, const struct sqe_submit *s, } static int io_write(struct io_kiocb *req, const struct sqe_submit *s, - bool force_nonblock) + bool force_nonblock, struct io_kiocb **nxt) { struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; struct kiocb *kiocb = &req->rw; @@ -1465,7 +1515,7 @@ static int io_write(struct io_kiocb *req, const struct sqe_submit *s, else ret2 = loop_rw_iter(WRITE, file, kiocb, &iter); if (!force_nonblock || ret2 != -EAGAIN) { - io_rw_done(kiocb, ret2); + call_io_rw_done(kiocb, ret2, nxt, s->needs_lock); } else { /* * If ->needs_lock is true, we're already in async @@ -1968,7 +2018,8 @@ static int io_req_defer(struct io_ring_ctx *ctx, struct io_kiocb *req, } static int __io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req, - const struct sqe_submit *s, bool force_nonblock) + const struct sqe_submit *s, bool force_nonblock, + struct io_kiocb **nxt) { int ret, opcode; @@ -1985,18 +2036,18 @@ static int __io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req, case IORING_OP_READV: if (unlikely(s->sqe->buf_index)) return -EINVAL; - ret = io_read(req, s, force_nonblock); + ret = io_read(req, s, force_nonblock, nxt); break; case IORING_OP_WRITEV: if (unlikely(s->sqe->buf_index)) return -EINVAL; - ret = io_write(req, s, force_nonblock); + ret = io_write(req, s, force_nonblock, nxt); break; case IORING_OP_READ_FIXED: - ret = io_read(req, s, force_nonblock); + ret = io_read(req, s, force_nonblock, nxt); break; case IORING_OP_WRITE_FIXED: - ret = io_write(req, s, force_nonblock); + ret = io_write(req, s, force_nonblock, nxt); break; case IORING_OP_FSYNC: ret = io_fsync(req, s->sqe, force_nonblock); @@ -2081,6 +2132,7 @@ static void io_sq_wq_submit_work(struct work_struct *work) struct sqe_submit *s = &req->submit; const struct io_uring_sqe *sqe = s->sqe; unsigned int flags = req->flags; + struct io_kiocb *nxt = NULL; /* Ensure we clear previously set non-block flag */ req->rw.ki_flags &= ~IOCB_NOWAIT; @@ -2101,7 +2153,7 @@ static void io_sq_wq_submit_work(struct work_struct *work) s->has_user = cur_mm != NULL; s->needs_lock = true; do { - ret = __io_submit_sqe(ctx, req, s, false); + ret = __io_submit_sqe(ctx, req, s, false, &nxt); /* * We can get EAGAIN for polled IO even though * we're forcing a sync submission from here, @@ -2125,6 +2177,12 @@ static void io_sq_wq_submit_work(struct work_struct *work) /* async context always use a copy of the sqe */ kfree(sqe); + /* if a dependent link is ready, do that as the next one */ + if (!ret && nxt) { + req = nxt; + continue; + } + /* req from defer and link list needn't decrease async cnt */ if (flags & (REQ_F_IO_DRAINED | REQ_F_LINK_DONE)) goto out; @@ -2271,7 +2329,7 @@ static int __io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req, { int ret; - ret = __io_submit_sqe(ctx, req, s, force_nonblock); + ret = __io_submit_sqe(ctx, req, s, force_nonblock, NULL); if (ret == -EAGAIN && !(req->flags & REQ_F_NOWAIT)) { struct io_uring_sqe *sqe_copy; -- Jens Axboe
