- 23 Oct, 2021 1 commit
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Hao Xu authored
The current logic of requests with IOSQE_ASYNC is first queueing it to io-worker, then execute it in a synchronous way. For unbound works like pollable requests(e.g. read/write a socketfd), the io-worker may stuck there waiting for events for a long time. And thus other works wait in the list for a long time too. Let's introduce a new way for unbound works (currently pollable requests), with this a request will first be queued to io-worker, then executed in a nonblock try rather than a synchronous way. Failure of that leads it to arm poll stuff and then the worker can begin to handle other works. The detail process of this kind of requests is: step1: original context: queue it to io-worker step2: io-worker context: nonblock try(the old logic is a synchronous try here) | |--fail--> arm poll | |--(fail/ready)-->synchronous issue | |--(succeed)-->worker finish it's job, tw take over the req This works much better than the old IOSQE_ASYNC logic in cases where unbound max_worker is relatively small. In this case, number of io-worker eazily increments to max_worker, new worker cannot be created and running workers stuck there handling old works in IOSQE_ASYNC mode. In my 64-core machine, set unbound max_worker to 20, run echo-server, turns out: (arguments: register_file, connetion number is 1000, message size is 12 Byte) original IOSQE_ASYNC: 76664.151 tps after this patch: 166934.985 tps Suggested-by:Jens Axboe <axboe@kernel.dk> Signed-off-by:
Hao Xu <haoxu@linux.alibaba.com> Link: https://lore.kernel.org/r/20211018133445.103438-1-haoxu@linux.alibaba.comSigned-off-by:
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- 20 Oct, 2021 2 commits
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Changcheng Deng authored
Use ERR_CAST() instead of ERR_PTR(PTR_ERR()). This makes it more readable and also fix this warning detected by err_cast.cocci: ./fs/io_uring.c: WARNING: 3208: 11-18: ERR_CAST can be used with buf Reported-by:
Zeal Robot <zealci@zte.com.cn> Signed-off-by:
Changcheng Deng <deng.changcheng@zte.com.cn> Link: https://lore.kernel.org/r/20211020084948.1038420-1-deng.changcheng@zte.com.cnSigned-off-by:
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Hao Xu authored
Currently force_nonblock stands for three meanings: - nowait or not - in an io-worker or not(hold uring_lock or not) Let's split the logic to two flags, IO_URING_F_NONBLOCK and IO_URING_F_UNLOCKED for convenience of the next patch. Suggested-by:
Pavel Begunkov <asml.silence@gmail.com> Signed-off-by:
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- 19 Oct, 2021 37 commits
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Arnd Bergmann authored
When enabling -Wunused warnings by building with W=1, I get an instance of the -Wunused-but-set-parameter warning in the io_uring code: fs/io_uring.c: In function 'io_queue_async_work': fs/io_uring.c:1445:61: error: parameter 'locked' set but not used [-Werror=unused-but-set-parameter] 1445 | static void io_queue_async_work(struct io_kiocb *req, bool *locked) | ~~~~~~^~~~~~ There are very few warnings of this type, so it would be nice to enable this by default and fix all the existing instances. As the assignment serves no purpose by itself other than to prevent developers from using the variable, an easy workaround is to remove the assignment and just rename the argument to "dont_use". Fixes: f237c30a ("io_uring: batch task work locking") Link: https://lore.kernel.org/lkml/20210920121352.93063-1-arnd@kernel.org/Signed-off-by:Arnd Bergmann <arnd@arndb.de> Link: https://lore.kernel.org/r/20211019153507.348480-1-arnd@kernel.orgSigned-off-by:
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Jens Axboe authored
The block layer can use this knowledge to make smarter decisions on how to handle the request, if it knows that N more may be coming. Switch to using blk_start_plug_nr_ios() to pass in that information. Signed-off-by: -
Pavel Begunkov authored
Make sure that REQ_F_SUPPORT_NOWAIT is always set io_prep_rw(), and so we can stop caring about setting it down the line simplifying io_file_supports_nowait(). Signed-off-by:
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Pavel Begunkov authored
Merge REQ_F_NOWAIT_READ and REQ_F_NOWAIT_WRITE into one flag, i.e. REQ_F_SUPPORT_NOWAIT. First it gets rid of dependence on CONFIG_64BIT but also simplifies the code. One thing to consider is when we don't have ->{read,write}_iter and go through loop_rw_iter(). Just fail it with -EAGAIN if we expect nowait behaviour but not sure whether it supports it. Signed-off-by: -
Pavel Begunkov authored
Don't check if we can do nowait before arming apoll, there are several reasons for that. First, we don't care much about files that don't support nowait. Second, it may be useful -- we don't want to be taking away extra workers from io-wq when it can go in some async. Even if it will go through io-wq eventually, it make difference in the numbers of workers actually used. And the last one, it's needed to clean nowait in future commits. [kernel test robot: fix unused-var] Signed-off-by:
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Noah Goldstein authored
This commit reorders the conditions in a branch in io_write. The reorder to check 'ret2 == -EAGAIN' first as checking '(req->ctx->flags & IORING_SETUP_IOPOLL)' will likely be more expensive due to 2x memory derefences. Signed-off-by:
Noah Goldstein <goldstein.w.n@gmail.com> Link: https://lore.kernel.org/r/20211017013229.4124279-1-goldstein.w.n@gmail.comSigned-off-by:
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Pavel Begunkov authored
We already store req->file in a variable in io_prep_rw(), just use it instead of a couple of left references to kicob->ki_filp. Signed-off-by:
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Pavel Begunkov authored
Move fixed rw io_req_set_rsrc_node() from rw prep into io_import_fixed(), if we're using fixed buffers it will always be called during submission as we save the state in advance, Signed-off-by:
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Pavel Begunkov authored
We pass iovec** into __io_import_iovec(), which should keep it, initialise and modify accordingly. It's expensive, return it directly from __io_import_iovec encoding errors with ERR_PTR if needed. io_import_iovec keeps the old interface, but it's inline and so everything is optimised nicely. Signed-off-by:
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Pavel Begunkov authored
Delay loading req->rw.{addr,len} in io_import_iovec until it's really needed, so removing extra loads for the fixed path, which doesn't use them. Signed-off-by: -
Pavel Begunkov authored
Don't decide about locking based on io_wq_current_is_worker(), it's not consistent with all other code and is expensive, use issue_flags. Signed-off-by:
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Pavel Begunkov authored
Don't load req->ctx in advance, it takes an extra register and the field stays valid even after opcode handlers. It also optimises out req->ctx load in io_iopoll_req_issued() once it's inlined. Signed-off-by:
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Pavel Begunkov authored
Combine force_nonblock branches (which is already optimised by compiler), flip branches so the most hot/common path is the first, e.g. as with non on-stack iov setup, and add extra likely/unlikely attributions for errror paths. Signed-off-by:
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Pavel Begunkov authored
Make io_import_iovec taking struct io_rw_state instead of an iter pointer. First it takes care of initialising iovec pointer, which can be forgotten. Even more, we can not init it if not needed, e.g. in case of IORING_OP_READ_FIXED or IORING_OP_READ. Also hide saving iter_state inside of it by splitting out an inline function of it to avoid extra ifs. Signed-off-by:
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Pavel Begunkov authored
First, change IO_URING_F_NONBLOCK to take sign bit of the int, so checking for it can be turned into test + sign-based-jump, makes the binary smaller and may be faster. Then, instead of passing need_lock boolean into io_import_iovec() just give it issue_flags, which is already stored somewhere. Saves some space on stack, a couple of test + cmov operations and other conversions. note: we still leave force_nonblock = issue_flags & IO_URING_F_NONBLOCK variable, but it's optimised out by the compiler into testing issue_flags directly. Signed-off-by:
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Pavel Begunkov authored
Currently io_read() and io_write() keep separate pointers to an iter and to struct iov_iter_state, which is not great for register spilling and requires more on-stack copies. They are both either on-stack or in req->async_data at the same time, so use struct io_rw_state and keep a pointer only to it, so having all the state with just one pointer. Signed-off-by:
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Pavel Begunkov authored
Add a new struct io_rw_state storing all iov related bits: fast iov, iterator and iterator state. Not much changes here, simply convert struct io_async_rw to use it. Signed-off-by:
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Pavel Begunkov authored
Don't override req->result in io_complete_rw_iopoll() when it's already of the same value, we have an if just above it, so move the assignment there. Also, add one simle unlikely() in __io_complete_rw_common(). Signed-off-by:
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Pavel Begunkov authored
Rearrange io_read return handling so first we expect it completing successfully and only then checking for errors, which is a colder path. Signed-off-by:
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Pavel Begunkov authored
Some of the functions keep issue_flags as int, change those to unsigned. Signed-off-by:
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Pavel Begunkov authored
Apparently, percpu_ref_put/get() are expensive enough if done per request, get them in a batch and cache on the submission side to avoid getting it over and over again. Also, if we're completing under uring_lock, return refs back into the cache instead of perfcpu_ref_put(). Pretty similar to how we do tctx->cached_refs accounting, but fall back to normal putting when we already changed a rsrc node by the time of free. Signed-off-by:
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Pavel Begunkov authored
io_req_set_rsrc_node() reloads loads req->ctx, however it's already in registers in all use cases, so better to pass it as a parameter. Signed-off-by:
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Pavel Begunkov authored
[ 158.514382] WARNING: CPU: 5 PID: 15251 at fs/io_uring.c:1141 io_free_batch_list+0x269/0x360 [ 158.514426] RIP: 0010:io_free_batch_list+0x269/0x360 [ 158.514437] Call Trace: [ 158.514440] __io_submit_flush_completions+0xde/0x180 [ 158.514444] tctx_task_work+0x14a/0x220 [ 158.514447] task_work_run+0x64/0xa0 [ 158.514448] __do_sys_io_uring_enter+0x7c/0x970 [ 158.514450] __x64_sys_io_uring_enter+0x22/0x30 [ 158.514451] do_syscall_64+0x43/0x90 [ 158.514453] entry_SYSCALL_64_after_hwframe+0x44/0xae We should not touch request internals including req->comp_list.next after putting our ref if it's not final, e.g. we can start freeing requests from the free cache. Fixed: 62ca9cb93e7f8 ("io_uring: optimise io_free_batch_list()") Signed-off-by: -
Pavel Begunkov authored
task_work_add() takes care of waking up the thread, remove useless wake_up_process(). Signed-off-by:
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Pavel Begunkov authored
Looking at the assembly, the compiler decided to reload req->opcode in io_op_defs[opcode].needs_file instead of one it had in a register, so store it in a temp variable so it can be optimised out. Also move the personality block later, it's better for spilling/etc. as it only depends on @sqe, which we're keeping anyway. By the way, zero req->opcode if it over IORING_OP_LAST, not a problem, at the moment but is safer. Signed-off-by:
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Pavel Begunkov authored
struct io_submit_state's ->free_list and ->link are hotter and smaller than ->plug, place them first. Signed-off-by:
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Pavel Begunkov authored
Add extra wq flushing for fallback_work, that's not necessary but safer if invariants of io_fallback_req_func() change. Signed-off-by:
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Pavel Begunkov authored
Plugging is only needed with requests that also need a file, so hide plugging under a ->needs_file check. Also, place ->needs_file and ->plug bits into the same byte of io_op_defs, it may matter for compilers, e.g. only with the change a tested one decided to optimise two memory testb into a more with two register testb. Signed-off-by:
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Pavel Begunkov authored
CQE result is a 32-bit integer, so the functions generating CQEs are better to accept not long but ints. Convert io_cqring_fill_event() and other helpers. Signed-off-by:
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Pavel Begunkov authored
Inline io_poll_complete(), it's simple and doesn't have any particular purpose. Signed-off-by:
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Pavel Begunkov authored
There is only a single user of io_req_needs_clean() inline it. Signed-off-by:
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Pavel Begunkov authored
We keep struct io_completion only as a temporal storage of cflags, Place it in io_kiocb, it's cleaner, removes extra bits and even might be used for future optimisations. Signed-off-by:
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Pavel Begunkov authored
->async_data is a slow path, so it won't matter much if we do the clean up inside io_clean_op(). Moreover, in many cases it's allocated together with setting one or more of IO_REQ_CLEAN_FLAGS flags, so it'd go through io_clean_op() anyway. Control ->async_data allocation with a new flag REQ_F_ASYNC_DATA, so we can do all the maintainence under io_req_needs_clean() fast check. Signed-off-by:
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Pavel Begunkov authored
Delay reading the next node in io_free_batch_list(), allows the compiler to load the value a bit later improving register spilling in some cases. With gcc 11.1 it helped to move @task_refs variable from the stack to a register and optimises out a couple of per request instructions. Signed-off-by:
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Pavel Begunkov authored
Attribute cold functions so compilers can optimise them for size. It shrinks the binary by 2.5-3% text data bss dec hex filename 90670 14002 8 104680 198e8 ./fs/io_uring.o 88053 14002 8 102063 18eaf ./fs/io_uring.o Signed-off-by:
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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:
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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:
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