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![Stefan Roesch](/assets/img/avatar_default.png)
This adds the napi busy polling support in io_uring.c. It adds a new napi_list to the io_ring_ctx structure. This list contains the list of napi_id's that are currently enabled for busy polling. The list is synchronized by the new napi_lock spin lock. The current default napi busy polling time is stored in napi_busy_poll_to. If napi busy polling is not enabled, the value is 0. In addition there is also a hash table. The hash table store the napi id and the pointer to the above list nodes. The hash table is used to speed up the lookup to the list elements. The hash table is synchronized with rcu. The NAPI_TIMEOUT is stored as a timeout to make sure that the time a napi entry is stored in the napi list is limited. The busy poll timeout is also stored as part of the io_wait_queue. This is necessary as for sq polling the poll interval needs to be adjusted and the napi callback allows only to pass in one value. This has been tested with two simple programs from the liburing library repository: the napi client and the napi server program. The client sends a request, which has a timestamp in its payload and the server replies with the same payload. The client calculates the roundtrip time and stores it to calculate the results. The client is running on host1 and the server is running on host 2 (in the same rack). The measured times below are roundtrip times. They are average times over 5 runs each. Each run measures 1 million roundtrips. no rx coal rx coal: frames=88,usecs=33 Default 57us 56us client_poll=100us 47us 46us server_poll=100us 51us 46us client_poll=100us+ 40us 40us server_poll=100us client_poll=100us+ 41us 39us server_poll=100us+ prefer napi busy poll on client client_poll=100us+ 41us 39us server_poll=100us+ prefer napi busy poll on server client_poll=100us+ 41us 39us server_poll=100us+ prefer napi busy poll on client + server Signed-off-by: Stefan Roesch <shr@devkernel.io> Suggested-by: Olivier Langlois <olivier@trillion01.com> Acked-by: Jakub Kicinski <kuba@kernel.org> Link: https://lore.kernel.org/r/20230608163839.2891748-5-shr@devkernel.io Signed-off-by: Jens Axboe <axboe@kernel.dk>
15 lines
477 B
Makefile
15 lines
477 B
Makefile
# SPDX-License-Identifier: GPL-2.0
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#
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# Makefile for io_uring
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obj-$(CONFIG_IO_URING) += io_uring.o xattr.o nop.o fs.o splice.o \
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sync.o advise.o filetable.o \
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openclose.o uring_cmd.o epoll.o \
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statx.o net.o msg_ring.o timeout.o \
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sqpoll.o fdinfo.o tctx.o poll.o \
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cancel.o kbuf.o rsrc.o rw.o opdef.o \
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notif.o waitid.o register.o truncate.o
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obj-$(CONFIG_IO_WQ) += io-wq.o
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obj-$(CONFIG_FUTEX) += futex.o
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obj-$(CONFIG_NET_RX_BUSY_POLL) += napi.o
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