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 <axboe@xxxxxxxxx>
---
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
