Dylan Yudaken [Wed, 22 Jun 2022 13:40:23 +0000 (06:40 -0700)]
io_uring: lockless task list
With networking use cases we see contention on the spinlock used to
protect the task_list when multiple threads try and add completions at once.
Instead we can use a lockless list, and assume that the first caller to
add to the list is responsible for kicking off task work.
Pavel Begunkov [Tue, 21 Jun 2022 09:09:00 +0000 (10:09 +0100)]
io_uring: improve io_run_task_work()
Since SQPOLL now uses TWA_SIGNAL_NO_IPI, there won't be task work items
without TIF_NOTIFY_SIGNAL. Simplify io_run_task_work() by removing
task->task_works check. Even though looks it doesn't cause extra cache
bouncing, it's still nice to not touch it an extra time when it might be
not cached.
Pavel Begunkov [Mon, 20 Jun 2022 14:27:35 +0000 (15:27 +0100)]
io_uring: optimize io_uring_task layout
task_work bits of io_uring_task are split into two cache lines causing
extra cache bouncing, place them into a separate cache line. Also move
the most used submission path fields closer together, so there are hot.
Pavel Begunkov [Mon, 20 Jun 2022 00:26:01 +0000 (01:26 +0100)]
io_uring: add a warn_once for poll_find
io_poll_remove() expects poll_find() to search only for poll requests and
passes a flag for this. Just be a little bit extra cautious considering
lots of recent poll/cancellation changes and add a WARN_ON_ONCE checking
that we don't get an apoll'ed request.
Pavel Begunkov [Mon, 20 Jun 2022 00:26:00 +0000 (01:26 +0100)]
io_uring: consistent naming for inline completion
Improve naming of the inline/deferred completion helper so it's
consistent with it's *_post counterpart. Add some comments and extra
lockdeps to ensure the locking is done right.
Pavel Begunkov [Mon, 20 Jun 2022 00:25:57 +0000 (01:25 +0100)]
io_uring: add io_commit_cqring_flush()
Since __io_commit_cqring_flush users moved to different files, introduce
io_commit_cqring_flush() helper and encapsulate all flags testing details
inside.
Pavel Begunkov [Mon, 20 Jun 2022 00:25:56 +0000 (01:25 +0100)]
io_uring: introduce locking helpers for CQE posting
spin_lock(&ctx->completion_lock);
/* post CQEs */
io_commit_cqring(ctx);
spin_unlock(&ctx->completion_lock);
io_cqring_ev_posted(ctx);
We have many places repeating this sequence, and the three function
unlock section is not perfect from the maintainance perspective and also
makes it harder to add new locking/sync trick.
Introduce two helpers. io_cq_lock(), which is simple and only grabs
->completion_lock, and io_cq_unlock_post() encapsulating the three call
section.
Pavel Begunkov [Mon, 20 Jun 2022 00:25:55 +0000 (01:25 +0100)]
io_uring: hide eventfd assumptions in eventfd paths
Some io_uring-eventfd users assume that there won't be spurious wakeups.
That assumption has to be honoured by all io_cqring_ev_posted() callers,
which is inconvenient and from time to time leads to problems but should
be maintained to not break the userspace.
Instead of making the callers track whether a CQE was posted or not, hide
it inside io_eventfd_signal(). It saves ->cached_cq_tail it saw last time
and triggers the eventfd only when ->cached_cq_tail changed since then.
Pavel Begunkov [Mon, 20 Jun 2022 00:25:54 +0000 (01:25 +0100)]
io_uring: fix io_poll_remove_all clang warnings
clang complains on bitwise operations with bools, add a bit more
verbosity to better show that we want to call io_poll_remove_all_table()
twice but with different arguments.
Pavel Begunkov [Mon, 20 Jun 2022 00:25:52 +0000 (01:25 +0100)]
io_uring: fix multi ctx cancellation
io_uring_try_cancel_requests() loops until there is nothing left to do
with the ring, however there might be several rings and they might have
dependencies between them, e.g. via poll requests.
Instead of cancelling rings one by one, try to cancel them all and only
then loop over if we still potenially some work to do.
Pavel Begunkov [Sun, 19 Jun 2022 11:26:08 +0000 (12:26 +0100)]
io_uring: remove ->flush_cqes optimisation
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().
Jens Axboe [Sun, 19 Jun 2022 01:44:33 +0000 (19:44 -0600)]
io_uring: move a few private types to local headers
Commit 3a3d47fa9cfd ("io_uring: make io_uring_types.h public") moved
a bunch of io_uring types to a kernel wide header, so we could make
tracing a bit saner rather than pass in a ton of arguments.
However, there are a few types in there that are not really needed to
be system wide. Move the cancel data and mapped buffers back to the
appropriate io_uring local headers.
Pavel Begunkov [Thu, 16 Jun 2022 12:57:20 +0000 (13:57 +0100)]
io_uring: clean up tracing events
We have lots of trace events accepting an io_uring request and wanting
to print some of its fields like user_data, opcode, flags and so on.
However, as trace points were unaware of io_uring structures, we had to
pass all the fields as arguments. Teach trace/events/io_uring.h about
struct io_kiocb and stop the misery of passing a horde of arguments to
trace helpers.
Pavel Begunkov [Thu, 16 Jun 2022 12:57:18 +0000 (13:57 +0100)]
io_uring: kill extra io_uring_types.h includes
io_uring/io_uring.h already includes io_uring_types.h, no need to
include it every time. Kill it in a bunch of places, it prepares us for
following patches.
Pavel Begunkov [Fri, 17 Jun 2022 08:48:05 +0000 (09:48 +0100)]
io_uring: change ->cqe_cached invariant for CQE32
With IORING_SETUP_CQE32 ->cqe_cached doesn't store a real address but
rather an implicit offset into cqes. Store the real cqe pointer and
increment it accordingly if CQE32.
Pavel Begunkov [Fri, 17 Jun 2022 08:48:02 +0000 (09:48 +0100)]
io_uring: introduce io_req_cqe_overflow()
__io_fill_cqe_req() is hot and inlined, we want it to be as small as
possible. Add io_req_cqe_overflow() accepting only a request and doing
all overflow accounting, and replace with it two calls to 6 argument
io_cqring_event_overflow().
Hao Xu [Fri, 17 Jun 2022 05:04:29 +0000 (13:04 +0800)]
io_uring: kbuf: add comments for some tricky code
Add comments to explain why it is always under uring lock when
incrementing head in __io_kbuf_recycle. And rectify one comemnt about
kbuf consuming in iowq case.
Pavel Begunkov [Thu, 16 Jun 2022 09:22:12 +0000 (10:22 +0100)]
io_uring: mutex locked poll hashing
Currently we do two extra spin lock/unlock pairs to add a poll/apoll
request to the cancellation hash table and remove it from there.
On the submission side we often already hold ->uring_lock and tw
completion is likely to hold it as well. Add a second cancellation hash
table protected by ->uring_lock. In concerns for latency because of a
need to have the mutex locked on the completion side, use the new table
only in following cases:
1) IORING_SETUP_SINGLE_ISSUER: only one task grabs uring_lock, so there
is little to no contention and so the main tw hander will almost
always end up grabbing it before calling callbacks.
2) IORING_SETUP_SQPOLL: same as with single issuer, only one task is
a major user of ->uring_lock.
3) apoll: we normally grab the lock on the completion side anyway to
execute the request, so it's free.
Pavel Begunkov [Thu, 16 Jun 2022 09:22:08 +0000 (10:22 +0100)]
io_uring: add IORING_SETUP_SINGLE_ISSUER
Add a new IORING_SETUP_SINGLE_ISSUER flag and the userspace visible part
of it, i.e. put limitations of submitters. Also, don't allow it together
with IOPOLL as we're not going to put it to good use.
Pavel Begunkov [Thu, 16 Jun 2022 09:22:05 +0000 (10:22 +0100)]
io_uring: limit the number of cancellation buckets
Don't allocate to many hash/cancellation buckets, there might be too
many, clamp it to 8 bits, or 256 * 64B = 16KB. We don't usually have too
many requests, and 256 buckets should be enough, especially since we
do hash search only in the cancellation path.
Pavel Begunkov [Thu, 16 Jun 2022 09:22:03 +0000 (10:22 +0100)]
io_uring: pass poll_find lock back
Instead of using implicit knowledge of what is locked or not after
io_poll_find() and co returns, pass back a pointer to the locked
bucket if any. If set the user must to unlock the spinlock.
Hao Xu [Thu, 16 Jun 2022 09:22:02 +0000 (10:22 +0100)]
io_uring: switch cancel_hash to use per entry spinlock
Add a new io_hash_bucket structure so that each bucket in cancel_hash
has separate spinlock. Use per entry lock for cancel_hash, this removes
some completion lock invocation and remove contension between different
cancel_hash entries.
Pavel Begunkov [Thu, 16 Jun 2022 09:21:58 +0000 (10:21 +0100)]
io_uring: kill REQ_F_COMPLETE_INLINE
REQ_F_COMPLETE_INLINE is only needed to delay queueing into the
completion list to io_queue_sqe() as __io_req_complete() is inlined and
we don't want to bloat the kernel.
As now we complete in a more centralised fashion in io_issue_sqe() we
can get rid of the flag and queue to the list directly.
Pavel Begunkov [Thu, 16 Jun 2022 09:21:57 +0000 (10:21 +0100)]
io_uring: rw: delegate sync completions to core io_uring
io_issue_sqe() from the io_uring core knows how to complete requests
based on the returned error code, we can delegate io_read()/io_write()
completion to it. Make kiocb_done() to return the right completion
code and propagate it.
Pavel Begunkov [Wed, 15 Jun 2022 16:33:56 +0000 (17:33 +0100)]
io_uring: don't set REQ_F_COMPLETE_INLINE in tw
io_req_task_complete() enqueues requests for state completion itself, no
need for REQ_F_COMPLETE_INLINE, which is only serve the purpose of not
bloating the kernel.
Pavel Begunkov [Wed, 15 Jun 2022 16:33:54 +0000 (17:33 +0100)]
io_uring: never defer-complete multi-apoll
Luckily, nnobody completes multi-apoll requests outside the polling
functions, but don't set IO_URING_F_COMPLETE_DEFER in any case as
there is nobody who is catching REQ_F_COMPLETE_INLINE, and so will leak
requests if used.
Pavel Begunkov [Wed, 15 Jun 2022 16:33:49 +0000 (17:33 +0100)]
io_uring: better caching for ctx timeout fields
Following timeout fields access patterns, move all of them into a
separate cache line inside ctx, so they don't intervene with normal
completion caching, especially since timeout removals and completion
are separated and the later is done via tw.
It also sheds some bytes from io_ring_ctx, 1216B -> 1152B
Jens Axboe [Wed, 1 Jun 2022 18:36:42 +0000 (12:36 -0600)]
io_uring: deprecate epoll_ctl support
As far as we know, nobody ever adopted the epoll_ctl management via
io_uring. Deprecate it now with a warning, and plan on removing it in
a later kernel version. When we do remove it, we can revert the following
commits as well:
39220e8d4a2a ("eventpoll: support non-blocking do_epoll_ctl() calls") 58e41a44c488 ("eventpoll: abstract out epoll_ctl() handler")
Jens Axboe [Fri, 27 May 2022 16:55:07 +0000 (10:55 -0600)]
io_uring: add support for level triggered poll
By default, the POLL_ADD command does edge triggered poll - if we get
a non-zero mask on the initial poll attempt, we complete the request
successfully.
Support level triggered by always waiting for a notification, regardless
of whether or not the initial mask matches the file state.
Jens Axboe [Thu, 26 May 2022 02:31:09 +0000 (20:31 -0600)]
io_uring: move poll handling into its own file
Add a io_poll_issue() rather than export the general task_work locking
and io_issue_sqe(), and put the io_op_defs definition and structure into
a separate header file so that poll can use it.
Jens Axboe [Tue, 24 May 2022 21:21:00 +0000 (15:21 -0600)]
io_uring: handle completions in the core
Normally request handlers complete requests themselves, if they don't
return an error. For the latter case, the core will complete it for
them.
This is unhandy for pushing opcode handlers further out, as we don't
want a bunch of inline completion code and we don't want to make the
completion path slower than it is now.
Let the core handle any completion, unless the handler explicitly
asks us not to.
Jens Axboe [Tue, 24 May 2022 16:26:28 +0000 (10:26 -0600)]
io_uring: define a request type cleanup handler
This can move request type specific cleanup into a private handler,
removing the need for the core io_uring parts to know what types
they are dealing with.
projects / users / dwmw2 / linux.git / log