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Commit 75b28aff authored by Hristo Venev's avatar Hristo Venev Committed by Jens Axboe
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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: default avatarHristo Venev <hristo@venev.name>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 27c4d3a3
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Inline Side-by-side
Showing with 128 additions and 127 deletions
fs/io_uring.c
View file @ 75b28aff
......@@ -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);
......
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