From 75b28affdd6aed1c68073ef53907c7bd822aff84 Mon Sep 17 00:00:00 2001 From: Hristo Venev Date: Mon, 26 Aug 2019 17:23:46 +0000 Subject: [PATCH] io_uring: allocate the two rings together Both the sq and the cq rings have sizes just over a power of two, and the sq ring is significantly smaller. By bundling them in a single alllocation, we get the sq ring for free. This also means that IORING_OFF_SQ_RING and IORING_OFF_CQ_RING now mean the same thing. If we indicate this to userspace, we can save a mmap call. Signed-off-by: Hristo Venev Signed-off-by: Jens Axboe --- fs/io_uring.c | 255 +++++++++++++++++++++++++------------------------- 1 file changed, 128 insertions(+), 127 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 08d614c6b60e..17dfe57c57f8 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -84,27 +84,29 @@ struct io_uring { }; /* - * This data is shared with the application through the mmap at offset - * IORING_OFF_SQ_RING. + * This data is shared with the application through the mmap at offsets + * IORING_OFF_SQ_RING and IORING_OFF_CQ_RING. * * The offsets to the member fields are published through struct * io_sqring_offsets when calling io_uring_setup. */ -struct io_sq_ring { +struct io_rings { /* * Head and tail offsets into the ring; the offsets need to be * masked to get valid indices. * - * The kernel controls head and the application controls tail. + * The kernel controls head of the sq ring and the tail of the cq ring, + * and the application controls tail of the sq ring and the head of the + * cq ring. */ - struct io_uring r; + struct io_uring sq, cq; /* - * Bitmask to apply to head and tail offsets (constant, equals + * Bitmasks to apply to head and tail offsets (constant, equals * ring_entries - 1) */ - u32 ring_mask; - /* Ring size (constant, power of 2) */ - u32 ring_entries; + u32 sq_ring_mask, cq_ring_mask; + /* Ring sizes (constant, power of 2) */ + u32 sq_ring_entries, cq_ring_entries; /* * Number of invalid entries dropped by the kernel due to * invalid index stored in array @@ -117,7 +119,7 @@ struct io_sq_ring { * counter includes all submissions that were dropped reaching * the new SQ head (and possibly more). */ - u32 dropped; + u32 sq_dropped; /* * Runtime flags * @@ -127,43 +129,7 @@ struct io_sq_ring { * The application needs a full memory barrier before checking * for IORING_SQ_NEED_WAKEUP after updating the sq tail. */ - u32 flags; - /* - * Ring buffer of indices into array of io_uring_sqe, which is - * mmapped by the application using the IORING_OFF_SQES offset. - * - * This indirection could e.g. be used to assign fixed - * io_uring_sqe entries to operations and only submit them to - * the queue when needed. - * - * The kernel modifies neither the indices array nor the entries - * array. - */ - u32 array[]; -}; - -/* - * This data is shared with the application through the mmap at offset - * IORING_OFF_CQ_RING. - * - * The offsets to the member fields are published through struct - * io_cqring_offsets when calling io_uring_setup. - */ -struct io_cq_ring { - /* - * Head and tail offsets into the ring; the offsets need to be - * masked to get valid indices. - * - * The application controls head and the kernel tail. - */ - struct io_uring r; - /* - * Bitmask to apply to head and tail offsets (constant, equals - * ring_entries - 1) - */ - u32 ring_mask; - /* Ring size (constant, power of 2) */ - u32 ring_entries; + u32 sq_flags; /* * Number of completion events lost because the queue was full; * this should be avoided by the application by making sure @@ -177,7 +143,7 @@ struct io_cq_ring { * As completion events come in out of order this counter is not * ordered with any other data. */ - u32 overflow; + u32 cq_overflow; /* * Ring buffer of completion events. * @@ -185,7 +151,7 @@ struct io_cq_ring { * produced, so the application is allowed to modify pending * entries. */ - struct io_uring_cqe cqes[]; + struct io_uring_cqe cqes[] ____cacheline_aligned_in_smp; }; struct io_mapped_ubuf { @@ -215,8 +181,18 @@ struct io_ring_ctx { bool compat; bool account_mem; - /* SQ ring */ - struct io_sq_ring *sq_ring; + /* + * Ring buffer of indices into array of io_uring_sqe, which is + * mmapped by the application using the IORING_OFF_SQES offset. + * + * This indirection could e.g. be used to assign fixed + * io_uring_sqe entries to operations and only submit them to + * the queue when needed. + * + * The kernel modifies neither the indices array nor the entries + * array. + */ + u32 *sq_array; unsigned cached_sq_head; unsigned sq_entries; unsigned sq_mask; @@ -234,8 +210,6 @@ struct io_ring_ctx { struct completion sqo_thread_started; struct { - /* CQ ring */ - struct io_cq_ring *cq_ring; unsigned cached_cq_tail; unsigned cq_entries; unsigned cq_mask; @@ -244,6 +218,8 @@ struct io_ring_ctx { struct eventfd_ctx *cq_ev_fd; } ____cacheline_aligned_in_smp; + struct io_rings *rings; + /* * If used, fixed file set. Writers must ensure that ->refs is dead, * readers must ensure that ->refs is alive as long as the file* is @@ -430,7 +406,7 @@ static inline bool io_sequence_defer(struct io_ring_ctx *ctx, if ((req->flags & (REQ_F_IO_DRAIN|REQ_F_IO_DRAINED)) != REQ_F_IO_DRAIN) return false; - return req->sequence != ctx->cached_cq_tail + ctx->sq_ring->dropped; + return req->sequence != ctx->cached_cq_tail + ctx->rings->sq_dropped; } static struct io_kiocb *io_get_deferred_req(struct io_ring_ctx *ctx) @@ -451,11 +427,11 @@ static struct io_kiocb *io_get_deferred_req(struct io_ring_ctx *ctx) static void __io_commit_cqring(struct io_ring_ctx *ctx) { - struct io_cq_ring *ring = ctx->cq_ring; + struct io_rings *rings = ctx->rings; - if (ctx->cached_cq_tail != READ_ONCE(ring->r.tail)) { + if (ctx->cached_cq_tail != READ_ONCE(rings->cq.tail)) { /* order cqe stores with ring update */ - smp_store_release(&ring->r.tail, ctx->cached_cq_tail); + smp_store_release(&rings->cq.tail, ctx->cached_cq_tail); if (wq_has_sleeper(&ctx->cq_wait)) { wake_up_interruptible(&ctx->cq_wait); @@ -478,7 +454,7 @@ static void io_commit_cqring(struct io_ring_ctx *ctx) static struct io_uring_cqe *io_get_cqring(struct io_ring_ctx *ctx) { - struct io_cq_ring *ring = ctx->cq_ring; + struct io_rings *rings = ctx->rings; unsigned tail; tail = ctx->cached_cq_tail; @@ -487,11 +463,11 @@ static struct io_uring_cqe *io_get_cqring(struct io_ring_ctx *ctx) * control dependency is enough as we're using WRITE_ONCE to * fill the cq entry */ - if (tail - READ_ONCE(ring->r.head) == ring->ring_entries) + if (tail - READ_ONCE(rings->cq.head) == rings->cq_ring_entries) return NULL; ctx->cached_cq_tail++; - return &ring->cqes[tail & ctx->cq_mask]; + return &rings->cqes[tail & ctx->cq_mask]; } static void io_cqring_fill_event(struct io_ring_ctx *ctx, u64 ki_user_data, @@ -510,9 +486,9 @@ static void io_cqring_fill_event(struct io_ring_ctx *ctx, u64 ki_user_data, WRITE_ONCE(cqe->res, res); WRITE_ONCE(cqe->flags, 0); } else { - unsigned overflow = READ_ONCE(ctx->cq_ring->overflow); + unsigned overflow = READ_ONCE(ctx->rings->cq_overflow); - WRITE_ONCE(ctx->cq_ring->overflow, overflow + 1); + WRITE_ONCE(ctx->rings->cq_overflow, overflow + 1); } } @@ -679,11 +655,11 @@ static void io_put_req(struct io_kiocb *req) io_free_req(req); } -static unsigned io_cqring_events(struct io_cq_ring *ring) +static unsigned io_cqring_events(struct io_rings *rings) { /* See comment at the top of this file */ smp_rmb(); - return READ_ONCE(ring->r.tail) - READ_ONCE(ring->r.head); + return READ_ONCE(rings->cq.tail) - READ_ONCE(rings->cq.head); } /* @@ -836,7 +812,7 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, * If we do, we can potentially be spinning for commands that * already triggered a CQE (eg in error). */ - if (io_cqring_events(ctx->cq_ring)) + if (io_cqring_events(ctx->rings)) break; /* @@ -2205,15 +2181,15 @@ static void io_submit_state_start(struct io_submit_state *state, static void io_commit_sqring(struct io_ring_ctx *ctx) { - struct io_sq_ring *ring = ctx->sq_ring; + struct io_rings *rings = ctx->rings; - if (ctx->cached_sq_head != READ_ONCE(ring->r.head)) { + if (ctx->cached_sq_head != READ_ONCE(rings->sq.head)) { /* * Ensure any loads from the SQEs are done at this point, * since once we write the new head, the application could * write new data to them. */ - smp_store_release(&ring->r.head, ctx->cached_sq_head); + smp_store_release(&rings->sq.head, ctx->cached_sq_head); } } @@ -2227,7 +2203,8 @@ static void io_commit_sqring(struct io_ring_ctx *ctx) */ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) { - struct io_sq_ring *ring = ctx->sq_ring; + struct io_rings *rings = ctx->rings; + u32 *sq_array = ctx->sq_array; unsigned head; /* @@ -2240,10 +2217,10 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) */ head = ctx->cached_sq_head; /* make sure SQ entry isn't read before tail */ - if (head == smp_load_acquire(&ring->r.tail)) + if (head == smp_load_acquire(&rings->sq.tail)) return false; - head = READ_ONCE(ring->array[head & ctx->sq_mask]); + head = READ_ONCE(sq_array[head & ctx->sq_mask]); if (head < ctx->sq_entries) { s->index = head; s->sqe = &ctx->sq_sqes[head]; @@ -2253,7 +2230,7 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) /* drop invalid entries */ ctx->cached_sq_head++; - ring->dropped++; + rings->sq_dropped++; return false; } @@ -2366,7 +2343,7 @@ static int io_sq_thread(void *data) TASK_INTERRUPTIBLE); /* Tell userspace we may need a wakeup call */ - ctx->sq_ring->flags |= IORING_SQ_NEED_WAKEUP; + ctx->rings->sq_flags |= IORING_SQ_NEED_WAKEUP; /* make sure to read SQ tail after writing flags */ smp_mb(); @@ -2380,12 +2357,12 @@ static int io_sq_thread(void *data) schedule(); finish_wait(&ctx->sqo_wait, &wait); - ctx->sq_ring->flags &= ~IORING_SQ_NEED_WAKEUP; + ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP; continue; } finish_wait(&ctx->sqo_wait, &wait); - ctx->sq_ring->flags &= ~IORING_SQ_NEED_WAKEUP; + ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP; } i = 0; @@ -2477,10 +2454,10 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit) static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, const sigset_t __user *sig, size_t sigsz) { - struct io_cq_ring *ring = ctx->cq_ring; + struct io_rings *rings = ctx->rings; int ret; - if (io_cqring_events(ring) >= min_events) + if (io_cqring_events(rings) >= min_events) return 0; if (sig) { @@ -2496,12 +2473,12 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, return ret; } - ret = wait_event_interruptible(ctx->wait, io_cqring_events(ring) >= min_events); + ret = wait_event_interruptible(ctx->wait, io_cqring_events(rings) >= min_events); restore_saved_sigmask_unless(ret == -ERESTARTSYS); if (ret == -ERESTARTSYS) ret = -EINTR; - return READ_ONCE(ring->r.head) == READ_ONCE(ring->r.tail) ? ret : 0; + return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0; } static void __io_sqe_files_unregister(struct io_ring_ctx *ctx) @@ -2821,17 +2798,45 @@ static void *io_mem_alloc(size_t size) return (void *) __get_free_pages(gfp_flags, get_order(size)); } +static unsigned long rings_size(unsigned sq_entries, unsigned cq_entries, + size_t *sq_offset) +{ + struct io_rings *rings; + size_t off, sq_array_size; + + off = struct_size(rings, cqes, cq_entries); + if (off == SIZE_MAX) + return SIZE_MAX; + +#ifdef CONFIG_SMP + off = ALIGN(off, SMP_CACHE_BYTES); + if (off == 0) + return SIZE_MAX; +#endif + + sq_array_size = array_size(sizeof(u32), sq_entries); + if (sq_array_size == SIZE_MAX) + return SIZE_MAX; + + if (check_add_overflow(off, sq_array_size, &off)) + return SIZE_MAX; + + if (sq_offset) + *sq_offset = off; + + return off; +} + static unsigned long ring_pages(unsigned sq_entries, unsigned cq_entries) { - struct io_sq_ring *sq_ring; - struct io_cq_ring *cq_ring; - size_t bytes; + size_t pages; - bytes = struct_size(sq_ring, array, sq_entries); - bytes += array_size(sizeof(struct io_uring_sqe), sq_entries); - bytes += struct_size(cq_ring, cqes, cq_entries); + pages = (size_t)1 << get_order( + rings_size(sq_entries, cq_entries, NULL)); + pages += (size_t)1 << get_order( + array_size(sizeof(struct io_uring_sqe), sq_entries)); - return (bytes + PAGE_SIZE - 1) / PAGE_SIZE; + return pages; } static int io_sqe_buffer_unregister(struct io_ring_ctx *ctx) @@ -3076,9 +3081,8 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx) } #endif - io_mem_free(ctx->sq_ring); + io_mem_free(ctx->rings); io_mem_free(ctx->sq_sqes); - io_mem_free(ctx->cq_ring); percpu_ref_exit(&ctx->refs); if (ctx->account_mem) @@ -3099,10 +3103,10 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait) * io_commit_cqring */ smp_rmb(); - if (READ_ONCE(ctx->sq_ring->r.tail) - ctx->cached_sq_head != - ctx->sq_ring->ring_entries) + if (READ_ONCE(ctx->rings->sq.tail) - ctx->cached_sq_head != + ctx->rings->sq_ring_entries) mask |= EPOLLOUT | EPOLLWRNORM; - if (READ_ONCE(ctx->cq_ring->r.head) != ctx->cached_cq_tail) + if (READ_ONCE(ctx->rings->sq.head) != ctx->cached_cq_tail) mask |= EPOLLIN | EPOLLRDNORM; return mask; @@ -3147,14 +3151,12 @@ static int io_uring_mmap(struct file *file, struct vm_area_struct *vma) switch (offset) { case IORING_OFF_SQ_RING: - ptr = ctx->sq_ring; + case IORING_OFF_CQ_RING: + ptr = ctx->rings; break; case IORING_OFF_SQES: ptr = ctx->sq_sqes; break; - case IORING_OFF_CQ_RING: - ptr = ctx->cq_ring; - break; default: return -EINVAL; } @@ -3241,19 +3243,27 @@ static const struct file_operations io_uring_fops = { static int io_allocate_scq_urings(struct io_ring_ctx *ctx, struct io_uring_params *p) { - struct io_sq_ring *sq_ring; - struct io_cq_ring *cq_ring; - size_t size; + struct io_rings *rings; + size_t size, sq_array_offset; - sq_ring = io_mem_alloc(struct_size(sq_ring, array, p->sq_entries)); - if (!sq_ring) + size = rings_size(p->sq_entries, p->cq_entries, &sq_array_offset); + if (size == SIZE_MAX) + return -EOVERFLOW; + + rings = io_mem_alloc(size); + if (!rings) return -ENOMEM; - ctx->sq_ring = sq_ring; - sq_ring->ring_mask = p->sq_entries - 1; - sq_ring->ring_entries = p->sq_entries; - ctx->sq_mask = sq_ring->ring_mask; - ctx->sq_entries = sq_ring->ring_entries; + ctx->rings = rings; + ctx->sq_array = (u32 *)((char *)rings + sq_array_offset); + rings->sq_ring_mask = p->sq_entries - 1; + rings->cq_ring_mask = p->cq_entries - 1; + rings->sq_ring_entries = p->sq_entries; + rings->cq_ring_entries = p->cq_entries; + ctx->sq_mask = rings->sq_ring_mask; + ctx->cq_mask = rings->cq_ring_mask; + ctx->sq_entries = rings->sq_ring_entries; + ctx->cq_entries = rings->cq_ring_entries; size = array_size(sizeof(struct io_uring_sqe), p->sq_entries); if (size == SIZE_MAX) @@ -3263,15 +3273,6 @@ static int io_allocate_scq_urings(struct io_ring_ctx *ctx, if (!ctx->sq_sqes) return -ENOMEM; - cq_ring = io_mem_alloc(struct_size(cq_ring, cqes, p->cq_entries)); - if (!cq_ring) - return -ENOMEM; - - ctx->cq_ring = cq_ring; - cq_ring->ring_mask = p->cq_entries - 1; - cq_ring->ring_entries = p->cq_entries; - ctx->cq_mask = cq_ring->ring_mask; - ctx->cq_entries = cq_ring->ring_entries; return 0; } @@ -3375,21 +3376,21 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p) goto err; memset(&p->sq_off, 0, sizeof(p->sq_off)); - p->sq_off.head = offsetof(struct io_sq_ring, r.head); - p->sq_off.tail = offsetof(struct io_sq_ring, r.tail); - p->sq_off.ring_mask = offsetof(struct io_sq_ring, ring_mask); - p->sq_off.ring_entries = offsetof(struct io_sq_ring, ring_entries); - p->sq_off.flags = offsetof(struct io_sq_ring, flags); - p->sq_off.dropped = offsetof(struct io_sq_ring, dropped); - p->sq_off.array = offsetof(struct io_sq_ring, array); + p->sq_off.head = offsetof(struct io_rings, sq.head); + p->sq_off.tail = offsetof(struct io_rings, sq.tail); + p->sq_off.ring_mask = offsetof(struct io_rings, sq_ring_mask); + p->sq_off.ring_entries = offsetof(struct io_rings, sq_ring_entries); + p->sq_off.flags = offsetof(struct io_rings, sq_flags); + p->sq_off.dropped = offsetof(struct io_rings, sq_dropped); + p->sq_off.array = (char *)ctx->sq_array - (char *)ctx->rings; memset(&p->cq_off, 0, sizeof(p->cq_off)); - p->cq_off.head = offsetof(struct io_cq_ring, r.head); - p->cq_off.tail = offsetof(struct io_cq_ring, r.tail); - p->cq_off.ring_mask = offsetof(struct io_cq_ring, ring_mask); - p->cq_off.ring_entries = offsetof(struct io_cq_ring, ring_entries); - p->cq_off.overflow = offsetof(struct io_cq_ring, overflow); - p->cq_off.cqes = offsetof(struct io_cq_ring, cqes); + p->cq_off.head = offsetof(struct io_rings, cq.head); + p->cq_off.tail = offsetof(struct io_rings, cq.tail); + p->cq_off.ring_mask = offsetof(struct io_rings, cq_ring_mask); + p->cq_off.ring_entries = offsetof(struct io_rings, cq_ring_entries); + p->cq_off.overflow = offsetof(struct io_rings, cq_overflow); + p->cq_off.cqes = offsetof(struct io_rings, cqes); return ret; err: io_ring_ctx_wait_and_kill(ctx); -- 2.20.1