- 19 Oct, 2021 40 commits
-
-
Pavel Begunkov authored
Currenlty, we allocate one ctx reference per request at submission time and put them at free. It's batched and not so expensive but it still bloats the kernel, adds 2 function calls for rcu and adds some overhead for request counting in io_free_batch_list(). Always keep one reference with a request, even when it's freed and in io_uring request caches. There is extra work at ring exit / quiesce paths, which now need to put all cached requests. io_ring_exit_work() is already looping, so it's not a problem. Add hybrid-busy waiting to io_ctx_quiesce() as well for now. Signed-off-by:
Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/99613fbe396e80777228cde39bbda1aa8938554e.1633373302.git.asml.silence@gmail.comSigned-off-by:
Jens Axboe <axboe@kernel.dk>
-
Pavel Begunkov authored
->cq_wait and ->poll_wait and waken up in the same manner, use a single waitqueue for both of them. CQ waiters are queued exclusively, so wake up should first go over all pollers and that's what we need. Signed-off-by:
-
Pavel Begunkov authored
io_cqring_ev_posted() doesn't need to wake SQPOLL, it's either done by userspace or with task_work, but no action is required on request completion. Rip off bits waking it up in io_cqring_ev_posted(). Signed-off-by:
-
Pavel Begunkov authored
The invariant of io_wq_work_list is that it's empty IFF ->first is NULL, so no need to initially set ->last. With now having more users of the list it may play a role, i.e. used in each tw iteration and on every completion flushing. Signed-off-by:
-
Pavel Begunkov authored
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:
-
Pavel Begunkov authored
io_req_complete_state() is inlined and used in lots of places, so we want to keep it concise. Move adding a request into a completion batch list from io_req_complete_state() into the consumer, i.e. __io_queue_sqe(). before vs after text data bss dec hex filename 91894 14002 8 105904 19db0 ./fs/io_uring.o 91046 14002 8 105056 19a60 ./fs/io_uring.o Signed-off-by:
-
Pavel Begunkov authored
Add two extra unlikely() in io_submit_sqes() and one around io_req_needs_clean() to help the compiler to avoid extra jumps in hot paths. Signed-off-by:
-
Pavel Begunkov authored
We want ->comp_list in the second cacheline, which is hotter comparing to the 3rd. Swap the field with ->link, which is not as hot and controlled by flags and so not accessed unless there is a link. By the way add a couple of comments for io_kiocb fields. Signed-off-by:
-
Pavel Begunkov authored
For some reason non-off IORING_OP_TIMEOUT always fails links, it's pretty inconvenient and unnecessary limits chaining after it to hard linking, which is far from ideal, e.g. doesn't pair well with timeout cancellation. Add a flag forcing it to not fail links on -ETIME. Signed-off-by:
-
Pavel Begunkov authored
Hiding a pointer to a struct io_buffer in rw.addr is error prone. We have some place in io_kiocb, so keep kbuf's in a separate field without aliasing and risks of it being misused. Signed-off-by:
-
Pavel Begunkov authored
Move io_req_prep() call inside of io_init_req(), it simplifies a bit error handling for callers. Signed-off-by:
-
Pavel Begunkov authored
Never return from io_drain_req() but punt to tw if we've got there but it's a false positive and we shouldn't actually drain. Signed-off-by:
-
Pavel Begunkov authored
Add a helper io_init_req_drain for initialising requests with IOSQE_DRAIN set. Also move bits from preambule of io_drain_req() in there, because we already modify all the bits needed inside the helper. Signed-off-by:
-
Pavel Begunkov authored
Clear ->drain_active in two more cases where we check for a need of draining. It's not a bug, but still may lead to some extra requests being punted to io-wq, and that may be not desirable. Signed-off-by:
-
Pavel Begunkov authored
io_req_complete_state() calls io_clean_op() and it may be not entirely obvious, leave a comment. Signed-off-by:
-
Pavel Begunkov authored
->inflight_entry is not used anymore after converting everything to single linked lists, remove it. Also adjust io_kiocb layout, so all hot bits are in first 3 cachelines. Signed-off-by:
-
Pavel Begunkov authored
Put an explicit check for number of requests to submit. First, we can turn while into do-while and it generates better code, and second that if can be cheaper, e.g. by using CPU flags after sub in io_sqring_entries(). Signed-off-by:
-
Pavel Begunkov authored
If a request completed inline the result should only be zero, it's a grave error otherwise. So, when we see REQ_F_COMPLETE_INLINE it's not even necessary to check the return code, and the flag check can be moved earlier. It's one "if" less for inline completions, and same two checks for it normally completing (ret == 0). Those are two cases we care about the most. Signed-off-by:
-
Pavel Begunkov authored
Extract slow paths from __io_queue_sqe() into a function and inline the hot path. With that we have everything completely inlined on the submission path up until io_issue_sqe(). -> io_submit_sqes() -> io_submit_sqe() (inlined) -> io_queue_sqe() (inlined) -> __io_queue_sqe() (inlined) -> io_issue_sqe() Signed-off-by: -
Pavel Begunkov authored
We don't want the slow path of io_queue_sqe to be inlined, so extract a function from it. text data bss dec hex filename 91950 13986 8 105944 19dd8 ./fs/io_uring.o 91758 13986 8 105752 19d18 ./fs/io_uring.o Signed-off-by:
-
Pavel Begunkov authored
req->ctx->active_drain is a bit too expensive, partially because of two dereferences. Do a trick, if we see it set in io_init_req(), set REQ_F_FORCE_ASYNC and it automatically goes through a slower path where we can catch it. It's nearly free to do in io_init_req() because there is already ->restricted check and it's in the same byte of a bitmask. Signed-off-by:
-
Pavel Begunkov authored
There are two call sites of io_queue_sqe() in io_submit_sqe(), combine them into one, because io_queue_sqe() is inline and we don't want to bloat binary, and will become even bigger text data bss dec hex filename 92126 13986 8 106120 19e88 ./fs/io_uring.o 91966 13986 8 105960 19de8 ./fs/io_uring.o Signed-off-by:
-
Pavel Begunkov authored
Submission state and ctx and coupled together, no need to passs Signed-off-by:
-
Pavel Begunkov authored
io_free_batch_list() iterates all requests in the passed in list, so we don't really need to know the tail but can keep iterating until meet NULL. Just pass the first node into it and it will be enough. Signed-off-by:
-
Pavel Begunkov authored
We now have a single function for batched put of requests, just inline struct req_batch and all related helpers into it. Signed-off-by:
-
Pavel Begunkov authored
First, convert rest of iopoll bits to single linked lists, and also replace per-request list_add_tail() with splicing a part of slist. With that, use io_free_batch_list() to put/free requests. The main advantage of it is that it's now the only user of struct req_batch and friends, and so they can be inlined. The main overhead there was per-request call to not-inlined io_req_free_batch(), which is expensive enough. Signed-off-by:
-
Pavel Begunkov authored
Convert explicit barrier around iopoll_completed to smp_load_acquire() and smp_store_release(). Similar on the callback side, but replaces a single smp_rmb() with per-request smp_load_acquire(), neither imply any extra CPU ordering for x86. Use READ_ONCE as usual where it doesn't matter. Use it to move filling CQEs by iopoll earlier, that will be necessary to avoid traversing the list one extra time in the future. Suggested-by:
Bart Van Assche <bvanassche@acm.org> Signed-off-by:
-
Pavel Begunkov authored
Add a helper io_free_batch_list(), which takes a single linked list and puts/frees all requests from it in an efficient manner. Will be reused later. Signed-off-by:
-
Pavel Begunkov authored
Use single linked lists for keeping iopoll requests, takes less space, may be faster, but mostly will be of benefit for further patches. Signed-off-by:
-
Pavel Begunkov authored
The main loop of io_do_iopoll() iterates and does ->iopoll() until it meets a first completed request, then it continues from that position and splices requests to pass them through io_iopoll_complete(). Split the loop in two for clearness, iopolling and reaping completed requests from the list. Signed-off-by:
-
Pavel Begunkov authored
Replace struct list_head free_list serving for caching requests with singly linked stack, which is faster. Signed-off-by:
-
Pavel Begunkov authored
Apart from just using lists (i.e. io_wq_work_list), we also want to have stacks, which are a bit faster, and have some interoperability between them. Add a stack implementation based on io_wq_work_node and some helpers. Signed-off-by:
-
Pavel Begunkov authored
We have several of request allocation layers, remove the last one, which is the submit->reqs array, and always use submit->free_reqs instead. Signed-off-by:
-
Pavel Begunkov authored
Currently we collect requests for completion batching in an array. Replace them with a singly linked list. It's as fast as arrays but doesn't take some much space in ctx, and will be used in future patches. Signed-off-by:
-
Pavel Begunkov authored
Don't pass nr_events pointer around but return directly, it's less expensive than pointer increments. Signed-off-by:
-
Pavel Begunkov authored
We don't really need to pass the number of requests to complete into io_do_iopoll(), a flag whether to enforce non-spin mode is enough. Should be straightforward, maybe except io_iopoll_check(). We pass !min there, because we do never enter with the number of already reaped requests is larger than the specified @min, apart from the first iteration, where nr_events is 0 and so the final check should be identical. Signed-off-by:
-
Pavel Begunkov authored
Hint the compiler that it's not as likely to have creds different from current attached to a request. The current code generation is far from ideal, hopefully it can help to some compilers to remove duplicated jump tables and so. Signed-off-by:
-
Hao Xu authored
boolean value is good enough for io_alloc_async_data. Signed-off-by:
Hao Xu <haoxu@linux.alibaba.com> Link: https://lore.kernel.org/r/20210922101522.9179-1-haoxu@linux.alibaba.comSigned-off-by:
-
Pavel Begunkov authored
IOSQE_IO_DRAIN is quite marginal and we don't care too much about IOSQE_BUFFER_SELECT. Save to ifs and hide both of them under SQE_VALID_FLAGS check. Now we first check whether it uses a "safe" subset, i.e. without DRAIN and BUFFER_SELECT, and only if it's not true we test the rest of the flags. Signed-off-by:
-
Pavel Begunkov authored
Now completions are done from task context, that means that it's either the task itself, task_work or io-wq worker. In all those cases the ctx will be staying alive by mutexing, explicit referencing or req references by iowq. Remove extra ctx pinning from io_req_complete_post(). Signed-off-by:
-
