We unconditionally call blk_start_plug() when starting the IO
submission, but we only really should do that if we have more than 1
request to submit AND we're potentially dealing with block based storage
underneath. For any other type of request, it's just a waste of time to
do so.
Add a ->plug bit to io_op_def and set it for read/write requests. We
could make this more precise and check the file itself as well, but it
doesn't matter that much and would quickly become more expensive.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3e1774d3187c..60cd740e5e3e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -748,6 +748,8 @@ struct io_submit_state {
void *reqs[IO_IOPOLL_BATCH];
unsigned int free_reqs;
+ bool plug_started;
+
/*
* Batch completion logic
*/
@@ -780,6 +782,8 @@ struct io_op_def {
unsigned buffer_select : 1;
/* must always have async data allocated */
unsigned needs_async_data : 1;
+ /* should block plug */
+ unsigned plug : 1;
/* size of async data needed, if any */
unsigned short async_size;
unsigned work_flags;
@@ -793,6 +797,7 @@ static const struct io_op_def io_op_defs[] = {
.pollin = 1,
.buffer_select = 1,
.needs_async_data = 1,
+ .plug = 1,
.async_size = sizeof(struct io_async_rw),
.work_flags = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
},
@@ -802,6 +807,7 @@ static const struct io_op_def io_op_defs[] = {
.unbound_nonreg_file = 1,
.pollout = 1,
.needs_async_data = 1,
+ .plug = 1,
.async_size = sizeof(struct io_async_rw),
.work_flags = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |
IO_WQ_WORK_FSIZE,
@@ -814,6 +820,7 @@ static const struct io_op_def io_op_defs[] = {
.needs_file = 1,
.unbound_nonreg_file = 1,
.pollin = 1,
+ .plug = 1,
.async_size = sizeof(struct io_async_rw),
.work_flags = IO_WQ_WORK_BLKCG | IO_WQ_WORK_MM,
},
@@ -822,6 +829,7 @@ static const struct io_op_def io_op_defs[] = {
.hash_reg_file = 1,
.unbound_nonreg_file = 1,
.pollout = 1,
+ .plug = 1,
.async_size = sizeof(struct io_async_rw),
.work_flags = IO_WQ_WORK_BLKCG | IO_WQ_WORK_FSIZE |
IO_WQ_WORK_MM,
@@ -905,6 +913,7 @@ static const struct io_op_def io_op_defs[] = {
.unbound_nonreg_file = 1,
.pollin = 1,
.buffer_select = 1,
+ .plug = 1,
.async_size = sizeof(struct io_async_rw),
.work_flags = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
},
@@ -912,6 +921,7 @@ static const struct io_op_def io_op_defs[] = {
.needs_file = 1,
.unbound_nonreg_file = 1,
.pollout = 1,
+ .plug = 1,
.async_size = sizeof(struct io_async_rw),
.work_flags = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |
IO_WQ_WORK_FSIZE,
@@ -6534,7 +6544,8 @@ static void io_submit_state_end(struct io_submit_state *state)
{
if (!list_empty(&state->comp.list))
io_submit_flush_completions(&state->comp);
- blk_finish_plug(&state->plug);
+ if (state->plug_started)
+ blk_finish_plug(&state->plug);
io_state_file_put(state);
if (state->free_reqs)
kmem_cache_free_bulk(req_cachep, state->free_reqs, state->reqs);
@@ -6546,7 +6557,7 @@ static void io_submit_state_end(struct io_submit_state *state)
static void io_submit_state_start(struct io_submit_state *state,
struct io_ring_ctx *ctx, unsigned int max_ios)
{
- blk_start_plug(&state->plug);
+ state->plug_started = false;
state->comp.nr = 0;
INIT_LIST_HEAD(&state->comp.list);
state->comp.ctx = ctx;
@@ -6688,6 +6699,16 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
/* same numerical values with corresponding REQ_F_*, safe to copy */
req->flags |= sqe_flags;
+ /*
+ * Plug now if we have more than 1 IO left after this, and the target
+ * is potentially a read/write to block based storage.
+ */
+ if (!state->plug_started && state->ios_left > 1 &&
+ io_op_defs[req->opcode].plug) {
+ blk_start_plug(&state->plug);
+ state->plug_started = true;
+ }
+
if (!io_op_defs[req->opcode].needs_file)
return 0;
--
Jens Axboe
