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io_uring: optimise extra io_get_cqe null check

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If the cached cqe check passes in io_get_cqe*() it already means that
the cqe we return is valid and non-zero, however the compiler is unable
to optimise null checks like in io_fill_cqe_req().

Do a bit of trickery, return success/fail boolean from io_get_cqe*()
and store cqe in the cqe parameter. That makes it do the right thing,
erasing the check together with the introduced indirection.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/322ea4d3377d3d4efd8ae90ab8ed28a99f518210.1692916914.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2023-08-24 23:53:27 +01:00 committed by Jens Axboe
parent 20d6b63387
commit 59fbc409e7
2 changed files with 12 additions and 15 deletions
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7
io_uring/io_uring.c
View file

@ -683,10 +683,10 @@ static void __io_cqring_overflow_flush(struct io_ring_ctx *ctx)
io_cq_lock(ctx);
while (!list_empty(&ctx->cq_overflow_list)) {
struct io_uring_cqe *cqe = io_get_cqe_overflow(ctx, true);
struct io_uring_cqe *cqe;
struct io_overflow_cqe *ocqe;
if (!cqe)
if (!io_get_cqe_overflow(ctx, &cqe, true))
break;
ocqe = list_first_entry(&ctx->cq_overflow_list,
struct io_overflow_cqe, list);
@ -862,8 +862,7 @@ static bool io_fill_cqe_aux(struct io_ring_ctx *ctx, u64 user_data, s32 res,
* submission (by quite a lot). Increment the overflow count in
* the ring.
*/
cqe = io_get_cqe(ctx);
if (likely(cqe)) {
if (likely(io_get_cqe(ctx, &cqe))) {
trace_io_uring_complete(ctx, NULL, user_data, res, cflags, 0, 0);
WRITE_ONCE(cqe->user_data, user_data);

20
io_uring/io_uring.h
View file

@ -109,28 +109,27 @@ static inline void io_req_task_work_add(struct io_kiocb *req)
#define io_for_each_link(pos, head) \
for (pos = (head); pos; pos = pos->link)
static inline struct io_uring_cqe *io_get_cqe_overflow(struct io_ring_ctx *ctx,
bool overflow)
static inline bool io_get_cqe_overflow(struct io_ring_ctx *ctx,
struct io_uring_cqe **ret,
bool overflow)
{
struct io_uring_cqe *cqe;
io_lockdep_assert_cq_locked(ctx);
if (unlikely(ctx->cqe_cached >= ctx->cqe_sentinel)) {
if (unlikely(!io_cqe_cache_refill(ctx, overflow)))
return NULL;
return false;
}
cqe = ctx->cqe_cached;
*ret = ctx->cqe_cached;
ctx->cached_cq_tail++;
ctx->cqe_cached++;
if (ctx->flags & IORING_SETUP_CQE32)
ctx->cqe_cached++;
return cqe;
return true;
}
static inline struct io_uring_cqe *io_get_cqe(struct io_ring_ctx *ctx)
static inline bool io_get_cqe(struct io_ring_ctx *ctx, struct io_uring_cqe **ret)
{
return io_get_cqe_overflow(ctx, false);
return io_get_cqe_overflow(ctx, ret, false);
}
static inline bool io_fill_cqe_req(struct io_ring_ctx *ctx, struct io_kiocb *req)
@ -142,8 +141,7 @@ static inline bool io_fill_cqe_req(struct io_ring_ctx *ctx, struct io_kiocb *req
* submission (by quite a lot). Increment the overflow count in
* the ring.
*/
cqe = io_get_cqe(ctx);
if (unlikely(!cqe))
if (unlikely(!io_get_cqe(ctx, &cqe)))
return false;
if (trace_io_uring_complete_enabled())