Commit a33ae9ce authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe

io_uring: optimise request allocation

Even after fully inlining io_alloc_req() my compiler does a NULL check
in the path of successful allocation, no hacks like an empty dereference
help it. Restructure io_alloc_req() by splitting out refilling part, so
the compiler generate a slightly better binary.
Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/eda17571bdc7248d8e617b23e7132a5416e4680b.1633373302.git.asml.silence@gmail.comSigned-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent fff4e40e
......@@ -1912,18 +1912,17 @@ static bool io_flush_cached_reqs(struct io_ring_ctx *ctx)
* Because of that, io_alloc_req() should be called only under ->uring_lock
* and with extra caution to not get a request that is still worked on.
*/
static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
static bool __io_alloc_req_refill(struct io_ring_ctx *ctx)
__must_hold(&ctx->uring_lock)
{
struct io_submit_state *state = &ctx->submit_state;
gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
void *reqs[IO_REQ_ALLOC_BATCH];
struct io_wq_work_node *node;
struct io_kiocb *req;
int ret, i;
if (likely(state->free_list.next || io_flush_cached_reqs(ctx)))
goto got_req;
return true;
ret = kmem_cache_alloc_bulk(req_cachep, gfp, ARRAY_SIZE(reqs), reqs);
......@@ -1934,7 +1933,7 @@ static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
if (unlikely(ret <= 0)) {
reqs[0] = kmem_cache_alloc(req_cachep, gfp);
if (!reqs[0])
return NULL;
return false;
ret = 1;
}
......@@ -1944,8 +1943,21 @@ static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
io_preinit_req(req, ctx);
wq_stack_add_head(&req->comp_list, &state->free_list);
}
got_req:
node = wq_stack_extract(&state->free_list);
return true;
}
static inline bool io_alloc_req_refill(struct io_ring_ctx *ctx)
{
if (unlikely(!ctx->submit_state.free_list.next))
return __io_alloc_req_refill(ctx);
return true;
}
static inline struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
{
struct io_wq_work_node *node;
node = wq_stack_extract(&ctx->submit_state.free_list);
return container_of(node, struct io_kiocb, comp_list);
}
......@@ -7217,12 +7229,12 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
const struct io_uring_sqe *sqe;
struct io_kiocb *req;
req = io_alloc_req(ctx);
if (unlikely(!req)) {
if (unlikely(!io_alloc_req_refill(ctx))) {
if (!submitted)
submitted = -EAGAIN;
break;
}
req = io_alloc_req(ctx);
sqe = io_get_sqe(ctx);
if (unlikely(!sqe)) {
wq_stack_add_head(&req->comp_list, &ctx->submit_state.free_list);
......
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