diff options
| author | Hao Xu <haoxu@linux.alibaba.com> | 2021-06-28 05:37:30 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2021-06-30 14:15:40 -0600 |
| commit | 915b3dde9b72cb4f531b04208daafcd0a257b847 (patch) | |
| tree | 7c7d74779edb837045b006b3d657d6b0681d5a31 | |
| parent | 99ebe4efbd3882422db1fd6a1b477291ea8bdab7 (diff) | |
io_uring: spin in iopoll() only when reqs are in a single queue
We currently spin in iopoll() when requests to be iopolled are for
same file(device), while one device may have multiple hardware queues.
given an example:
hw_queue_0 | hw_queue_1
req(30us) req(10us)
If we first spin on iopolling for the hw_queue_0. the avg latency would
be (30us + 30us) / 2 = 30us. While if we do round robin, the avg
latency would be (30us + 10us) / 2 = 20us since we reap the request in
hw_queue_1 in time. So it's better to do spinning only when requests
are in same hardware queue.
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | fs/io_uring.c | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c index b14de92832e1..67099bb99a02 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -434,7 +434,7 @@ struct io_ring_ctx { struct list_head iopoll_list; struct hlist_head *cancel_hash; unsigned cancel_hash_bits; - bool poll_multi_file; + bool poll_multi_queue; } ____cacheline_aligned_in_smp; struct io_restriction restrictions; @@ -2314,7 +2314,7 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events, * Only spin for completions if we don't have multiple devices hanging * off our complete list, and we're under the requested amount. */ - spin = !ctx->poll_multi_file && *nr_events < min; + spin = !ctx->poll_multi_queue && *nr_events < min; ret = 0; list_for_each_entry_safe(req, tmp, &ctx->iopoll_list, inflight_entry) { @@ -2553,14 +2553,22 @@ static void io_iopoll_req_issued(struct io_kiocb *req) * different devices. */ if (list_empty(&ctx->iopoll_list)) { - ctx->poll_multi_file = false; - } else if (!ctx->poll_multi_file) { + ctx->poll_multi_queue = false; + } else if (!ctx->poll_multi_queue) { struct io_kiocb *list_req; + unsigned int queue_num0, queue_num1; list_req = list_first_entry(&ctx->iopoll_list, struct io_kiocb, inflight_entry); - if (list_req->file != req->file) - ctx->poll_multi_file = true; + + if (list_req->file != req->file) { + ctx->poll_multi_queue = true; + } else { + queue_num0 = blk_qc_t_to_queue_num(list_req->rw.kiocb.ki_cookie); + queue_num1 = blk_qc_t_to_queue_num(req->rw.kiocb.ki_cookie); + if (queue_num0 != queue_num1) + ctx->poll_multi_queue = true; + } } /* |