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io_uring: remove io_preinit_req()

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Apart from setting ->ctx, io_preinit_req() zeroes a bunch of fields of a
request, from which only ->file_node is mandatory. Remove the function
and zero the entire request on first allocation. With that, we also need
to initialise ->ctx every time, which might be a good thing for
performance as now we're likely overwriting the entire cache line, and
so it can write combined and avoid RMW.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ba5485dc913f1e275862ce88f5169d4ac4a33836.1746533807.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2025-05-06 13:31:07 +01:00 committed by Jens Axboe
parent 78967aabf6
commit 9c2ff3f9b5
2 changed files with 3 additions and 19 deletions
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21
io_uring/io_uring.c
View File

@ -927,22 +927,6 @@ void io_req_defer_failed(struct io_kiocb *req, s32 res)
io_req_complete_defer(req);
}
/*
* Don't initialise the fields below on every allocation, but do that in
* advance and keep them valid across allocations.
*/
static void io_preinit_req(struct io_kiocb *req, struct io_ring_ctx *ctx)
{
req->ctx = ctx;
req->buf_node = NULL;
req->file_node = NULL;
req->link = NULL;
req->async_data = NULL;
/* not necessary, but safer to zero */
memset(&req->cqe, 0, sizeof(req->cqe));
memset(&req->big_cqe, 0, sizeof(req->big_cqe));
}
/*
* A request might get retired back into the request caches even before opcode
* handlers and io_issue_sqe() are done with it, e.g. inline completion path.
@ -952,7 +936,7 @@ static void io_preinit_req(struct io_kiocb *req, struct io_ring_ctx *ctx)
__cold bool __io_alloc_req_refill(struct io_ring_ctx *ctx)
__must_hold(&ctx->uring_lock)
{
gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
gfp_t gfp = GFP_KERNEL | __GFP_NOWARN | __GFP_ZERO;
void *reqs[IO_REQ_ALLOC_BATCH];
int ret;
@ -973,7 +957,6 @@ __cold bool __io_alloc_req_refill(struct io_ring_ctx *ctx)
while (ret--) {
struct io_kiocb *req = reqs[ret];
io_preinit_req(req, ctx);
io_req_add_to_cache(req, ctx);
}
return true;
@ -2049,7 +2032,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
int personality;
u8 opcode;
/* req is partially pre-initialised, see io_preinit_req() */
req->ctx = ctx;
req->opcode = opcode = READ_ONCE(sqe->opcode);
/* same numerical values with corresponding REQ_F_*, safe to copy */
sqe_flags = READ_ONCE(sqe->flags);

1
io_uring/notif.c
View File

@ -112,6 +112,7 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
if (unlikely(!io_alloc_req(ctx, &notif)))
return NULL;
notif->ctx = ctx;
notif->opcode = IORING_OP_NOP;
notif->flags = 0;
notif->file = NULL;