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io_uring: add io-wq workqueue sharing

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If IORING_SETUP_ATTACH_WQ is set, it expects wq_fd in io_uring_params to
be a valid io_uring fd io-wq of which will be shared with the newly
created io_uring instance. If the flag is set but it can't share io-wq,
it fails.

This allows creation of "sibling" io_urings, where we prefer to keep the
SQ/CQ private, but want to share the async backend to minimize the amount
of overhead associated with having multiple rings that belong to the same
backend.

Reported-by: Jens Axboe <axboe@kernel.dk>
Reported-by: Daurnimator <quae@daurnimator.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2020-01-28 03:15:48 +03:00 committed by Jens Axboe
parent eba6f5a330
commit 24369c2e3b
2 changed files with 53 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
fs/io_uring.c
View File

@ -5704,11 +5704,56 @@ static void io_get_work(struct io_wq_work *work)
refcount_inc(&req->refs);
}
static int io_init_wq_offload(struct io_ring_ctx *ctx,
struct io_uring_params *p)
{
struct io_wq_data data;
struct fd f;
struct io_ring_ctx *ctx_attach;
unsigned int concurrency;
int ret = 0;
data.user = ctx->user;
data.get_work = io_get_work;
data.put_work = io_put_work;
if (!(p->flags & IORING_SETUP_ATTACH_WQ)) {
/* Do QD, or 4 * CPUS, whatever is smallest */
concurrency = min(ctx->sq_entries, 4 * num_online_cpus());
ctx->io_wq = io_wq_create(concurrency, &data);
if (IS_ERR(ctx->io_wq)) {
ret = PTR_ERR(ctx->io_wq);
ctx->io_wq = NULL;
}
return ret;
}
f = fdget(p->wq_fd);
if (!f.file)
return -EBADF;
if (f.file->f_op != &io_uring_fops) {
ret = -EINVAL;
goto out_fput;
}
ctx_attach = f.file->private_data;
/* @io_wq is protected by holding the fd */
if (!io_wq_get(ctx_attach->io_wq, &data)) {
ret = -EINVAL;
goto out_fput;
}
ctx->io_wq = ctx_attach->io_wq;
out_fput:
fdput(f);
return ret;
}
static int io_sq_offload_start(struct io_ring_ctx *ctx,
struct io_uring_params *p)
{
struct io_wq_data data;
unsigned concurrency;
int ret;
init_waitqueue_head(&ctx->sqo_wait);
@ -5752,18 +5797,9 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
goto err;
}
data.user = ctx->user;
data.get_work = io_get_work;
data.put_work = io_put_work;
/* Do QD, or 4 * CPUS, whatever is smallest */
concurrency = min(ctx->sq_entries, 4 * num_online_cpus());
ctx->io_wq = io_wq_create(concurrency, &data);
if (IS_ERR(ctx->io_wq)) {
ret = PTR_ERR(ctx->io_wq);
ctx->io_wq = NULL;
ret = io_init_wq_offload(ctx, p);
if (ret)
goto err;
}
return 0;
err:
@ -6589,7 +6625,7 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
if (p.flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL |
IORING_SETUP_SQ_AFF | IORING_SETUP_CQSIZE |
IORING_SETUP_CLAMP))
IORING_SETUP_CLAMP | IORING_SETUP_ATTACH_WQ))
return -EINVAL;
ret = io_uring_create(entries, &p);

4
include/uapi/linux/io_uring.h
View File

@ -75,6 +75,7 @@ enum {
#define IORING_SETUP_SQ_AFF (1U << 2) /* sq_thread_cpu is valid */
#define IORING_SETUP_CQSIZE (1U << 3) /* app defines CQ size */
#define IORING_SETUP_CLAMP (1U << 4) /* clamp SQ/CQ ring sizes */
#define IORING_SETUP_ATTACH_WQ (1U << 5) /* attach to existing wq */
enum {
IORING_OP_NOP,
@ -183,7 +184,8 @@ struct io_uring_params {
__u32 sq_thread_cpu;
__u32 sq_thread_idle;
__u32 features;
__u32 resv[4];
__u32 wq_fd;
__u32 resv[3];
struct io_sqring_offsets sq_off;
struct io_cqring_offsets cq_off;
};