From aa00f67adc2c0d6439f81b5a81ff181377c47a7e Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 22 Oct 2024 13:47:00 -0600 Subject: [PATCH] io_uring: add support for fixed wait regions Generally applications have 1 or a few waits of waiting, yet they pass in a struct io_uring_getevents_arg every time. This needs to get copied and, in turn, the timeout value needs to get copied. Rather than do this for every invocation, allow the application to register a fixed set of wait regions that can simply be indexed when asking the kernel to wait on events. At ring setup time, the application can register a number of these wait regions and initialize region/index 0 upfront: struct io_uring_reg_wait *reg; reg = io_uring_setup_reg_wait(ring, nr_regions, &ret); /* set timeout and mark as set, sigmask/sigmask_sz as needed */ reg->ts.tv_sec = 0; reg->ts.tv_nsec = 100000; reg->flags = IORING_REG_WAIT_TS; where nr_regions >= 1 && nr_regions <= PAGE_SIZE / sizeof(*reg). The above initializes index 0, but 63 other regions can be initialized, if needed. Now, instead of doing: struct __kernel_timespec timeout = { .tv_nsec = 100000, }; io_uring_submit_and_wait_timeout(ring, &cqe, nr, &t, NULL); to wait for events for each submit_and_wait, or just wait, operation, it can just reference the above region at offset 0 and do: io_uring_submit_and_wait_reg(ring, &cqe, nr, 0); to achieve the same goal of waiting 100usec without needing to copy both struct io_uring_getevents_arg (24b) and struct __kernel_timeout (16b) for each invocation. Struct io_uring_reg_wait looks as follows: struct io_uring_reg_wait { struct __kernel_timespec ts; __u32 min_wait_usec; __u32 flags; __u64 sigmask; __u32 sigmask_sz; __u32 pad[3]; __u64 pad2[2]; }; embedding the timeout itself in the region, rather than passing it as a pointer as well. Note that the signal mask is still passed as a pointer, both for compatability reasons, but also because there doesn't seem to be a lot of high frequency waits scenarios that involve setting and resetting the signal mask for each wait. The application is free to modify any region before a wait call, or it can use keep multiple regions with different settings to avoid needing to modify the same one for wait calls. Up to a page size of regions is mapped by default, allowing PAGE_SIZE / 64 available regions for use. The registered region must fit within a page. On a 4kb page size system, that allows for 64 wait regions if a full page is used, as the size of struct io_uring_reg_wait is 64b. The region registered must be aligned to io_uring_reg_wait in size. It's valid to register less than 64 entries. In network performance testing with zero-copy, this reduced the time spent waiting on the TX side from 3.12% to 0.3% and the RX side from 4.4% to 0.3%. Wait regions are fixed for the lifetime of the ring - once registered, they are persistent until the ring is torn down. The regions support minimum wait timeout as well as the regular waits. Signed-off-by: Jens Axboe --- include/linux/io_uring_types.h | 10 +++++ include/uapi/linux/io_uring.h | 41 +++++++++++++++++ io_uring/io_uring.c | 70 ++++++++++++++++++++++++----- io_uring/register.c | 82 ++++++++++++++++++++++++++++++++++ io_uring/register.h | 1 + 5 files changed, 192 insertions(+), 12 deletions(-) diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h index 841579dcdae9..2f12828b22a4 100644 --- a/include/linux/io_uring_types.h +++ b/include/linux/io_uring_types.h @@ -327,6 +327,14 @@ struct io_ring_ctx { atomic_t cq_wait_nr; atomic_t cq_timeouts; struct wait_queue_head cq_wait; + + /* + * If registered with IORING_REGISTER_CQWAIT_REG, a single + * page holds N entries, mapped in cq_wait_arg. cq_wait_index + * is the maximum allowable index. + */ + struct io_uring_reg_wait *cq_wait_arg; + unsigned char cq_wait_index; } ____cacheline_aligned_in_smp; /* timeouts */ @@ -430,6 +438,8 @@ struct io_ring_ctx { unsigned short n_sqe_pages; struct page **ring_pages; struct page **sqe_pages; + + struct page **cq_wait_page; }; struct io_tw_state { diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 60b9c98595fa..65b7417c1b05 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -518,6 +518,7 @@ struct io_cqring_offsets { #define IORING_ENTER_EXT_ARG (1U << 3) #define IORING_ENTER_REGISTERED_RING (1U << 4) #define IORING_ENTER_ABS_TIMER (1U << 5) +#define IORING_ENTER_EXT_ARG_REG (1U << 6) /* * Passed in for io_uring_setup(2). Copied back with updated info on success @@ -620,6 +621,9 @@ enum io_uring_register_op { /* resize CQ ring */ IORING_REGISTER_RESIZE_RINGS = 33, + /* register fixed io_uring_reg_wait arguments */ + IORING_REGISTER_CQWAIT_REG = 34, + /* this goes last */ IORING_REGISTER_LAST, @@ -803,6 +807,43 @@ enum io_uring_register_restriction_op { IORING_RESTRICTION_LAST }; +enum { + IORING_REG_WAIT_TS = (1U << 0), +}; + +/* + * Argument for IORING_REGISTER_CQWAIT_REG, registering a region of + * struct io_uring_reg_wait that can be indexed when io_uring_enter(2) is + * called rather than pass in a wait argument structure separately. + */ +struct io_uring_cqwait_reg_arg { + __u32 flags; + __u32 struct_size; + __u32 nr_entries; + __u32 pad; + __u64 user_addr; + __u64 pad2[3]; +}; + +/* + * Argument for io_uring_enter(2) with + * IORING_GETEVENTS | IORING_ENTER_EXT_ARG_REG set, where the actual argument + * is an index into a previously registered fixed wait region described by + * the below structure. + */ +struct io_uring_reg_wait { + struct __kernel_timespec ts; + __u32 min_wait_usec; + __u32 flags; + __u64 sigmask; + __u32 sigmask_sz; + __u32 pad[3]; + __u64 pad2[2]; +}; + +/* + * Argument for io_uring_enter(2) with IORING_GETEVENTS | IORING_ENTER_EXT_ARG + */ struct io_uring_getevents_arg { __u64 sigmask; __u32 sigmask_sz; diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 4cd0ee52710d..2863b957e373 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2736,6 +2736,7 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx) io_alloc_cache_free(&ctx->msg_cache, io_msg_cache_free); io_futex_cache_free(ctx); io_destroy_buffers(ctx); + io_unregister_cqwait_reg(ctx); mutex_unlock(&ctx->uring_lock); if (ctx->sq_creds) put_cred(ctx->sq_creds); @@ -3224,21 +3225,43 @@ void __io_uring_cancel(bool cancel_all) io_uring_cancel_generic(cancel_all, NULL); } -static int io_validate_ext_arg(unsigned flags, const void __user *argp, size_t argsz) +static struct io_uring_reg_wait *io_get_ext_arg_reg(struct io_ring_ctx *ctx, + const struct io_uring_getevents_arg __user *uarg) { - if (flags & IORING_ENTER_EXT_ARG) { - struct io_uring_getevents_arg arg; + struct io_uring_reg_wait *arg = READ_ONCE(ctx->cq_wait_arg); - if (argsz != sizeof(arg)) - return -EINVAL; - if (copy_from_user(&arg, argp, sizeof(arg))) - return -EFAULT; + if (arg) { + unsigned int index = (unsigned int) (uintptr_t) uarg; + + if (index <= ctx->cq_wait_index) + return arg + index; } + + return ERR_PTR(-EFAULT); +} + +static int io_validate_ext_arg(struct io_ring_ctx *ctx, unsigned flags, + const void __user *argp, size_t argsz) +{ + struct io_uring_getevents_arg arg; + + if (!(flags & IORING_ENTER_EXT_ARG)) + return 0; + + if (flags & IORING_ENTER_EXT_ARG_REG) { + if (argsz != sizeof(struct io_uring_reg_wait)) + return -EINVAL; + return PTR_ERR(io_get_ext_arg_reg(ctx, argp)); + } + if (argsz != sizeof(arg)) + return -EINVAL; + if (copy_from_user(&arg, argp, sizeof(arg))) + return -EFAULT; return 0; } -static int io_get_ext_arg(unsigned flags, const void __user *argp, - struct ext_arg *ext_arg) +static int io_get_ext_arg(struct io_ring_ctx *ctx, unsigned flags, + const void __user *argp, struct ext_arg *ext_arg) { const struct io_uring_getevents_arg __user *uarg = argp; struct io_uring_getevents_arg arg; @@ -3252,6 +3275,28 @@ static int io_get_ext_arg(unsigned flags, const void __user *argp, return 0; } + if (flags & IORING_ENTER_EXT_ARG_REG) { + struct io_uring_reg_wait *w; + + if (ext_arg->argsz != sizeof(struct io_uring_reg_wait)) + return -EINVAL; + w = io_get_ext_arg_reg(ctx, argp); + if (IS_ERR(w)) + return PTR_ERR(w); + + if (w->flags & ~IORING_REG_WAIT_TS) + return -EINVAL; + ext_arg->min_time = READ_ONCE(w->min_wait_usec) * NSEC_PER_USEC; + ext_arg->sig = u64_to_user_ptr(READ_ONCE(w->sigmask)); + ext_arg->argsz = READ_ONCE(w->sigmask_sz); + if (w->flags & IORING_REG_WAIT_TS) { + ext_arg->ts.tv_sec = READ_ONCE(w->ts.tv_sec); + ext_arg->ts.tv_nsec = READ_ONCE(w->ts.tv_nsec); + ext_arg->ts_set = true; + } + return 0; + } + /* * EXT_ARG is set - ensure we agree on the size of it and copy in our * timespec and sigset_t pointers if good. @@ -3297,7 +3342,8 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, if (unlikely(flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP | IORING_ENTER_SQ_WAIT | IORING_ENTER_EXT_ARG | IORING_ENTER_REGISTERED_RING | - IORING_ENTER_ABS_TIMER))) + IORING_ENTER_ABS_TIMER | + IORING_ENTER_EXT_ARG_REG))) return -EINVAL; /* @@ -3380,7 +3426,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, */ mutex_lock(&ctx->uring_lock); iopoll_locked: - ret2 = io_validate_ext_arg(flags, argp, argsz); + ret2 = io_validate_ext_arg(ctx, flags, argp, argsz); if (likely(!ret2)) { min_complete = min(min_complete, ctx->cq_entries); @@ -3390,7 +3436,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, } else { struct ext_arg ext_arg = { .argsz = argsz }; - ret2 = io_get_ext_arg(flags, argp, &ext_arg); + ret2 = io_get_ext_arg(ctx, flags, argp, &ext_arg); if (likely(!ret2)) { min_complete = min(min_complete, ctx->cq_entries); diff --git a/io_uring/register.c b/io_uring/register.c index fc6c94d694b2..1eb686eaa310 100644 --- a/io_uring/register.c +++ b/io_uring/register.c @@ -570,6 +570,82 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg) return ret; } +void io_unregister_cqwait_reg(struct io_ring_ctx *ctx) +{ + unsigned short npages = 1; + + if (!ctx->cq_wait_page) + return; + + io_pages_unmap(ctx->cq_wait_arg, &ctx->cq_wait_page, &npages, true); + ctx->cq_wait_arg = NULL; + if (ctx->user) + __io_unaccount_mem(ctx->user, 1); +} + +/* + * Register a page holding N entries of struct io_uring_reg_wait, which can + * be used via io_uring_enter(2) if IORING_GETEVENTS_EXT_ARG_REG is set. + * If that is set with IORING_GETEVENTS_EXT_ARG, then instead of passing + * in a pointer for a struct io_uring_getevents_arg, an index into this + * registered array is passed, avoiding two (arg + timeout) copies per + * invocation. + */ +static int io_register_cqwait_reg(struct io_ring_ctx *ctx, void __user *uarg) +{ + struct io_uring_cqwait_reg_arg arg; + struct io_uring_reg_wait *reg; + struct page **pages; + unsigned long len; + int nr_pages, poff; + int ret; + + if (ctx->cq_wait_page || ctx->cq_wait_arg) + return -EBUSY; + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + if (!arg.nr_entries || arg.flags) + return -EINVAL; + if (arg.struct_size != sizeof(*reg)) + return -EINVAL; + if (check_mul_overflow(arg.struct_size, arg.nr_entries, &len)) + return -EOVERFLOW; + if (len > PAGE_SIZE) + return -EINVAL; + /* offset + len must fit within a page, and must be reg_wait aligned */ + poff = arg.user_addr & ~PAGE_MASK; + if (len + poff > PAGE_SIZE) + return -EINVAL; + if (poff % arg.struct_size) + return -EINVAL; + + pages = io_pin_pages(arg.user_addr, len, &nr_pages); + if (IS_ERR(pages)) + return PTR_ERR(pages); + ret = -EINVAL; + if (nr_pages != 1) + goto out_free; + if (ctx->user) { + ret = __io_account_mem(ctx->user, 1); + if (ret) + goto out_free; + } + + reg = vmap(pages, 1, VM_MAP, PAGE_KERNEL); + if (reg) { + ctx->cq_wait_index = arg.nr_entries - 1; + WRITE_ONCE(ctx->cq_wait_page, pages); + WRITE_ONCE(ctx->cq_wait_arg, (void *) reg + poff); + return 0; + } + ret = -ENOMEM; + if (ctx->user) + __io_unaccount_mem(ctx->user, 1); +out_free: + io_pages_free(&pages, nr_pages); + return ret; +} + static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, void __user *arg, unsigned nr_args) __releases(ctx->uring_lock) @@ -764,6 +840,12 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, break; ret = io_register_resize_rings(ctx, arg); break; + case IORING_REGISTER_CQWAIT_REG: + ret = -EINVAL; + if (!arg || nr_args != 1) + break; + ret = io_register_cqwait_reg(ctx, arg); + break; default: ret = -EINVAL; break; diff --git a/io_uring/register.h b/io_uring/register.h index a5f39d5ef9e0..3e935e8fa4b2 100644 --- a/io_uring/register.h +++ b/io_uring/register.h @@ -5,5 +5,6 @@ int io_eventfd_unregister(struct io_ring_ctx *ctx); int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id); struct file *io_uring_register_get_file(unsigned int fd, bool registered); +void io_unregister_cqwait_reg(struct io_ring_ctx *ctx); #endif