mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-26 06:35:04 +07:00
2b188cc1bb
The submission queue (SQ) and completion queue (CQ) rings are shared between the application and the kernel. This eliminates the need to copy data back and forth to submit and complete IO. IO submissions use the io_uring_sqe data structure, and completions are generated in the form of io_uring_cqe data structures. The SQ ring is an index into the io_uring_sqe array, which makes it possible to submit a batch of IOs without them being contiguous in the ring. The CQ ring is always contiguous, as completion events are inherently unordered, and hence any io_uring_cqe entry can point back to an arbitrary submission. Two new system calls are added for this: io_uring_setup(entries, params) Sets up an io_uring instance for doing async IO. On success, returns a file descriptor that the application can mmap to gain access to the SQ ring, CQ ring, and io_uring_sqes. io_uring_enter(fd, to_submit, min_complete, flags, sigset, sigsetsize) Initiates IO against the rings mapped to this fd, or waits for them to complete, or both. The behavior is controlled by the parameters passed in. If 'to_submit' is non-zero, then we'll try and submit new IO. If IORING_ENTER_GETEVENTS is set, the kernel will wait for 'min_complete' events, if they aren't already available. It's valid to set IORING_ENTER_GETEVENTS and 'min_complete' == 0 at the same time, this allows the kernel to return already completed events without waiting for them. This is useful only for polling, as for IRQ driven IO, the application can just check the CQ ring without entering the kernel. With this setup, it's possible to do async IO with a single system call. Future developments will enable polled IO with this interface, and polled submission as well. The latter will enable an application to do IO without doing ANY system calls at all. For IRQ driven IO, an application only needs to enter the kernel for completions if it wants to wait for them to occur. Each io_uring is backed by a workqueue, to support buffered async IO as well. We will only punt to an async context if the command would need to wait for IO on the device side. Any data that can be accessed directly in the page cache is done inline. This avoids the slowness issue of usual threadpools, since cached data is accessed as quickly as a sync interface. Sample application: http://git.kernel.dk/cgit/fio/plain/t/io_uring.c Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
96 lines
1.9 KiB
C
96 lines
1.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
|
|
/*
|
|
* Header file for the io_uring interface.
|
|
*
|
|
* Copyright (C) 2019 Jens Axboe
|
|
* Copyright (C) 2019 Christoph Hellwig
|
|
*/
|
|
#ifndef LINUX_IO_URING_H
|
|
#define LINUX_IO_URING_H
|
|
|
|
#include <linux/fs.h>
|
|
#include <linux/types.h>
|
|
|
|
/*
|
|
* IO submission data structure (Submission Queue Entry)
|
|
*/
|
|
struct io_uring_sqe {
|
|
__u8 opcode; /* type of operation for this sqe */
|
|
__u8 flags; /* as of now unused */
|
|
__u16 ioprio; /* ioprio for the request */
|
|
__s32 fd; /* file descriptor to do IO on */
|
|
__u64 off; /* offset into file */
|
|
__u64 addr; /* pointer to buffer or iovecs */
|
|
__u32 len; /* buffer size or number of iovecs */
|
|
union {
|
|
__kernel_rwf_t rw_flags;
|
|
__u32 __resv;
|
|
};
|
|
__u64 user_data; /* data to be passed back at completion time */
|
|
__u64 __pad2[3];
|
|
};
|
|
|
|
#define IORING_OP_NOP 0
|
|
#define IORING_OP_READV 1
|
|
#define IORING_OP_WRITEV 2
|
|
|
|
/*
|
|
* IO completion data structure (Completion Queue Entry)
|
|
*/
|
|
struct io_uring_cqe {
|
|
__u64 user_data; /* sqe->data submission passed back */
|
|
__s32 res; /* result code for this event */
|
|
__u32 flags;
|
|
};
|
|
|
|
/*
|
|
* Magic offsets for the application to mmap the data it needs
|
|
*/
|
|
#define IORING_OFF_SQ_RING 0ULL
|
|
#define IORING_OFF_CQ_RING 0x8000000ULL
|
|
#define IORING_OFF_SQES 0x10000000ULL
|
|
|
|
/*
|
|
* Filled with the offset for mmap(2)
|
|
*/
|
|
struct io_sqring_offsets {
|
|
__u32 head;
|
|
__u32 tail;
|
|
__u32 ring_mask;
|
|
__u32 ring_entries;
|
|
__u32 flags;
|
|
__u32 dropped;
|
|
__u32 array;
|
|
__u32 resv1;
|
|
__u64 resv2;
|
|
};
|
|
|
|
struct io_cqring_offsets {
|
|
__u32 head;
|
|
__u32 tail;
|
|
__u32 ring_mask;
|
|
__u32 ring_entries;
|
|
__u32 overflow;
|
|
__u32 cqes;
|
|
__u64 resv[2];
|
|
};
|
|
|
|
/*
|
|
* io_uring_enter(2) flags
|
|
*/
|
|
#define IORING_ENTER_GETEVENTS (1U << 0)
|
|
|
|
/*
|
|
* Passed in for io_uring_setup(2). Copied back with updated info on success
|
|
*/
|
|
struct io_uring_params {
|
|
__u32 sq_entries;
|
|
__u32 cq_entries;
|
|
__u32 flags;
|
|
__u32 resv[7];
|
|
struct io_sqring_offsets sq_off;
|
|
struct io_cqring_offsets cq_off;
|
|
};
|
|
|
|
#endif
|