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io_uring: remove ->flush_cqes optimisation

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It's not clear how widely used IOSQE_CQE_SKIP_SUCCESS is, and how often
->flush_cqes flag prevents from completion being flushed. Sometimes it's
high level of concurrency that enables it at least for one CQE, but
sometimes it doesn't save much because nobody waiting on the CQ.

Remove ->flush_cqes flag and the optimisation, it should benefit the
normal use case. Note, that there is no spurious eventfd problem with
that as checks for spuriousness were incorporated into
io_eventfd_signal().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/692e81eeddccc096f449a7960365fa7b4a18f8e6.1655637157.git.asml.silence@gmail.com
[axboe: remove now dead state->flush_cqes variable]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2022-06-19 12:26:08 +01:00 committed by Jens Axboe
parent a830ffd287
commit d9dee4302a
3 changed files with 10 additions and 16 deletions
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1
include/linux/io_uring_types.h
View File

@ -148,7 +148,6 @@ struct io_submit_state {
bool plug_started;
bool need_plug;
bool flush_cqes;
unsigned short submit_nr;
struct blk_plug plug;
};

23
io_uring/io_uring.c
View File

@ -1250,22 +1250,19 @@ static void __io_submit_flush_completions(struct io_ring_ctx *ctx)
struct io_wq_work_node *node, *prev;
struct io_submit_state *state = &ctx->submit_state;
if (state->flush_cqes) {
spin_lock(&ctx->completion_lock);
wq_list_for_each(node, prev, &state->compl_reqs) {
struct io_kiocb *req = container_of(node, struct io_kiocb,
comp_list);
spin_lock(&ctx->completion_lock);
wq_list_for_each(node, prev, &state->compl_reqs) {
struct io_kiocb *req = container_of(node, struct io_kiocb,
comp_list);
if (!(req->flags & REQ_F_CQE_SKIP))
__io_fill_cqe_req(ctx, req);
}
io_commit_cqring(ctx);
spin_unlock(&ctx->completion_lock);
io_cqring_ev_posted(ctx);
state->flush_cqes = false;
if (!(req->flags & REQ_F_CQE_SKIP))
__io_fill_cqe_req(ctx, req);
}
io_commit_cqring(ctx);
spin_unlock(&ctx->completion_lock);
io_cqring_ev_posted(ctx);
io_free_batch_list(ctx, state->compl_reqs.first);
INIT_WQ_LIST(&state->compl_reqs);
}

2
io_uring/io_uring.h
View File

@ -219,8 +219,6 @@ static inline void io_req_add_compl_list(struct io_kiocb *req)
{
struct io_submit_state *state = &req->ctx->submit_state;
if (!(req->flags & REQ_F_CQE_SKIP))
state->flush_cqes = true;
wq_list_add_tail(&req->comp_list, &state->compl_reqs);
}