- 15 Jun, 2021 19 commits
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Pavel Begunkov authored
In most cases io_commit_cqring() is just an smp_store_release(), and it's hot enough, especially for IRQ rw, to want it to save on a function call. Mark it inline and extract a non-inlined slow path doing drain and timeout flushing. The inlined part is pretty slim to not cause binary bloating. Signed-off-by:
Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/7350f8b6b92caa50a48a80be39909f0d83eddd93.1623772051.git.asml.silence@gmail.comSigned-off-by:
Jens Axboe <axboe@kernel.dk>
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Pavel Begunkov authored
Place all drain_next logic into io_drain_req(), so it's never executed if there was no drained requests before. The only thing we need is to set ->drain_active if we see a request with IOSQE_IO_DRAIN, do that in io_init_req() where flags are definitely in registers. Also, all drain-related code is encapsulated in io_drain_req(), makes it cleaner. Signed-off-by:
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Pavel Begunkov authored
->drain_used is one way, which is not optimal if users use DRAIN but very rarely. However, we can just clear it in io_drain_req() when all drained before requests are gone. Also rename the flag to reflect the change and be more clear about it. Signed-off-by:
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Pavel Begunkov authored
fs/io_uring.c: In function 'io_alloc_page_table': include/linux/minmax.h:20:28: warning: comparison of distinct pointer types lacks a cast Cast everything to size_t using min_t. Reported-by:
Stephen Rothwell <sfr@canb.auug.org.au> Fixes: 9123c8ff ("io_uring: add helpers for 2 level table alloc") Signed-off-by:
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Fam Zheng authored
The sqe_ptr argument has been gone since 709b302f (io_uring: simplify io_get_sqring, 2020-04-08), made the return value of the function. Update the comment accordingly. Signed-off-by:
Fam Zheng <fam.zheng@bytedance.com> Reviewed-by:
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Pavel Begunkov authored
Replace drain checks with one-way flag set upon seeing the first IOSQE_IO_DRAIN request. There are several places where it cuts cycles well: 1) It's much faster than the fast check with two conditions in io_drain_req() including pretty complex list_empty_careful(). 2) We can mark io_queue_sqe() inline now, that's a huge win. 3) It replaces timeout and drain checks in io_commit_cqring() with a single flags test. Also great not touching ->defer_list there without a reason so limiting cache bouncing. It adds a small amount of overhead to drain path, but it's negligible. The main nuisance is that once it meets any DRAIN request in io_uring instance lifetime it will _always_ go through a slower path, so drain-less and offset-mode timeout less applications are preferable. The overhead in that case would be not big, but it's worth to bear in mind. Signed-off-by:
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Pavel Begunkov authored
Rename io_req_defer() into io_drain_req() and refactor it uncoupling it from io_queue_sqe() error handling and preparing for coming optimisations. Also, prioritise non IOSQE_ASYNC path. Signed-off-by:
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Pavel Begunkov authored
->uring_lock is prevalently used for submission, even though it protects many other things like iopoll, registeration, selected bufs, and more. And it's placed together with ->cq_wait poked on completion and CQ waiting sides. Move them apart, ->uring_lock goes to the submission data, and cq_wait to completion related chunk. The last one requires some reshuffling so everything needed by io_cqring_ev_posted*() is in one cacheline. Signed-off-by:
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Pavel Begunkov authored
We use several wait_queue_head's for different purposes, but namings are confusing. First rename ctx->cq_wait into ctx->poll_wait, because this one is used for polling an io_uring instance. Then rename ctx->wait into ctx->cq_wait, which is responsible for CQE waiting. Signed-off-by:
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Pavel Begunkov authored
There are no users of ->sq_check_overflow, only ->cq_check_overflow is used. Combine it and move out of completion related part of struct io_ring_ctx. A not so obvious benefit of it is fitting all completion side fields into a single cacheline. It was taking 2 lines before with 56B padding, and io_cqring_ev_posted*() were still touching both of them. Signed-off-by:
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Pavel Begunkov authored
submit_state.link is used only to assemble a link and not used for actual submission, so clear it before io_queue_sqe() in io_submit_sqe(), awhile it's hot and in caches and queueing doesn't spoil it. May also potentially help compiler with spilling or to do other optimisations. Signed-off-by:
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Pavel Begunkov authored
io_commit_cqring() might be very hot and we definitely don't want to touch ->timeout_list there, because 1) it's shared with the submission side so might lead to cache bouncing and 2) may need to load an extra cache line, especially for IRQ completions. We're interested in it at the completion side only when there are offset-mode timeouts, which are not so popular. Replace list_empty(->timeout_list) hot path check with a new one-way flag, which is set when we prepare the first offset-mode timeout. note: the flag sits in the same line as briefly used after ->rings Signed-off-by:
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Pavel Begunkov authored
Kill ->cached_sq_dropped and wire DRAIN sequence number correction via ->cq_extra, which is there exactly for that purpose. User visible dropped counter will be populated by incrementing it instead of keeping a copy, similarly as it was done not so long ago with cq_overflow. Signed-off-by:
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Pavel Begunkov authored
The line of io_get_sqe() evaluating @head consists of too many operations including READ_ONCE(), it's not convenient for probing. Refactor it also improving readability. Signed-off-by:
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Pavel Begunkov authored
Since moving locked_free_* out of struct io_submit_state ctx->submit_state is accessed on submission side only, so move it into the submission section. Same goes for rsrc table pointers/nodes/etc., they must be taken and checked during submission because sync'ed by uring_lock, so move them there as well. Signed-off-by:
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Pavel Begunkov authored
ctx->flags are heavily used by both, completion and submission sides, so move it out from the ctx fields related to submissions. Instead, place it together with ctx->refs, because it's already cacheline-aligned and so pads lots of space, and both almost never change. Also, in most occasions they are accessed together as refs are taken at submission time and put back during completion. Do same with ctx->rings, where the pointer itself is never modified apart from ring init/free. Note: in percpu mode, struct percpu_ref doesn't modify the struct itself but takes indirection with ref->percpu_count_ptr. Signed-off-by:
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Pavel Begunkov authored
sq_array and sq_sqes are always used together, however they are in different cachelines, where the borderline is right before cq_overflow_list is rather rarely touched. Move the fields together so it loads only one cacheline. Signed-off-by:
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Colin Ian King authored
The variable ret is being initialized with a value that is never read, the assignment is redundant and can be removed. Addresses-Coverity: ("Unused value") Signed-off-by:Colin Ian King <colin.king@canonical.com> Link: https://lore.kernel.org/r/20210615143424.60449-1-colin.king@canonical.comSigned-off-by:
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Colin Ian King authored
Static analysis is warning that the sizeof being used is should be of *data->tags[i] and not data->tags[i]. Although these are the same size on 64 bit systems it is not a portable assumption to assume this is true for all cases. Fix this by using a temporary pointer tag_slot to make the code a clearer. Addresses-Coverity: ("Sizeof not portable") Fixes: d878c816 ("io_uring: hide rsrc tag copy into generic helpers") Signed-off-by:
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- 14 Jun, 2021 21 commits
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Pavel Begunkov authored
There are only two calls in source code of io_iter_do_read(), the function is small and pretty hot though is failed to get inlined. Makr it as inline. Signed-off-by:
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Pavel Begunkov authored
Merge io_uring_cancel_sqpoll() and __io_uring_cancel() as it's easier to have a conditional ctx traverse inside than keeping them in sync. Signed-off-by:
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Pavel Begunkov authored
tctx in submission part is always synchronised because is executed from the task's context, so we can batch allocate tctx/task references and store them across syscall boundaries. It avoids enough of operations, including an atomic for getting task ref and a percpu_counter_add() function call, which still fallback to spinlock for large batching cases (around >=32). Should be good for SQPOLL submitting in small portions and coming at some moment bpf submissions. Signed-off-by:
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Pavel Begunkov authored
We don't really need vmalloc for keeping tags, it's not a hot path and is there out of convenience, so replace it with two level tables to not litter kernel virtual memory mappings. Signed-off-by:
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Pavel Begunkov authored
Some parts like fixed file table use 2 level tables, factor out helpers for allocating/deallocating them as more users are to come. Signed-off-by:
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Pavel Begunkov authored
io_rsrc_put_work() is executed by workqueue in non-irq context, so no need for irqsave/restore variants of spinlocking. Signed-off-by:
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Pavel Begunkov authored
Make io_rsrc_data_alloc() taking care of rsrc tags loading on registration, so we don't need to repeat it for each new rsrc type. Signed-off-by:
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Pavel Begunkov authored
io_worker_handle_work() already takes care of the empty list case and releases spinlock, so get rid of ugly conditional unlocking and unconditionally call handle_work() Signed-off-by:
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Pavel Begunkov authored
io_wqe_worker()'s main loop does check IO_WQ_BIT_EXIT flag, so no need for a second test_bit at the end as it will immediately jump to the first check afterwards. Signed-off-by:
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Pavel Begunkov authored
What at some moment was references to struct file used to control lifetimes of task/ctx is now just internal tctx structures/nodes, so rename outdated *task_file() routines into something more sensible. Signed-off-by:
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Pavel Begunkov authored
A simple refactoring of io_iopoll_req_issued(), move in_async inside so we don't pass it around and save on double checking it. Signed-off-by:
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Pavel Begunkov authored
iowq->refs is initialised to one and killed on exit, so it's not used and we can kill it. Signed-off-by:
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Pavel Begunkov authored
io-wq keeps an array of pointers to struct io_wqe, allocate this array as a part of struct io-wq, it's easier to code and saves an extra indirection for nearly each io-wq call. Signed-off-by:
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Pavel Begunkov authored
There is a complaint against sys_io_uring_enter() blocking if it submits stdin reads. The problem is in __io_file_supports_async(), which sees that it's a cdev and allows it to be processed inline. Punt char devices using generic rules of io_file_supports_async(), including checking for presence of *_iter() versions of rw callbacks. Apparently, it will affect most of cdevs with some exceptions like null and zero devices. Cc: stable@vger.kernel.org Reported-by:
Birk Hirdman <lonjil@gmail.com> Signed-off-by:
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Pavel Begunkov authored
Relax buffer registration restictions, which filters out file backed memory, and allow shmem/memfd as they have normal anonymous pages underneath. Signed-off-by:
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Pavel Begunkov authored
struct io_submit_state contains struct io_comp_state and so locked_free_*, that renders cachelines around ->locked_free* being invalidated on most non-inline completions, that may terrorise caches if submissions and completions are done by different tasks. Signed-off-by:
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Pavel Begunkov authored
Rename io_get_cqring() into io_get_cqe() for consistency with SQ, and just because the old name is not as clear. Signed-off-by:
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Pavel Begunkov authored
There are two copies of cq_overflow, shared with userspace and internal cached one. It was needed for DRAIN accounting, but now we have yet another knob to tune the accounting, i.e. cq_extra, and we can throw away the internal counter and just increment the one in the shared ring. If user modifies it as so never gets the right overflow value ever again, it's its problem, even though before we would have restored it back by next overflow. Signed-off-by:
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Pavel Begunkov authored
No need to cache cq_mask, it's exactly cq_entries - 1, so just deduce it to not carry it around. Signed-off-by:
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Pavel Begunkov authored
We have numbers of {sq,cq} entries cached in ctx, don't look up them in user-shared rings as 1) it may fetch additional cacheline 2) user may change it and so it's always error prone. Signed-off-by: -
Pavel Begunkov authored
ring has two types of resource-related fields: used for request submission, and field needed for update/registration. Reshuffle them into these two groups for better locality and readability. The second group is not in the hot path, so it's natural to place them somewhere in the end. Also update an outdated comment. Signed-off-by:
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