On 2/22/24 10:40 PM, David Wei wrote:
> diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
> index bd7071aeec5d..57318fc01379 100644
> --- a/include/linux/io_uring_types.h
> +++ b/include/linux/io_uring_types.h
> @@ -425,6 +425,9 @@ struct io_ring_ctx {
> DECLARE_HASHTABLE(napi_ht, 4);
> #endif
>
> + /* iowait accounting */
> + bool iowait_enabled;
> +
Since this is just a single bit, you should put it in the top section
where we have other single bits for hot / read-mostly data. This avoids
needing something many cache lines away for the hotter wait path, and it
avoids growing the struct as there's still plenty of space there for
this.
> diff --git a/io_uring/register.c b/io_uring/register.c
> index 99c37775f974..7cbc08544c4c 100644
> --- a/io_uring/register.c
> +++ b/io_uring/register.c
> @@ -387,6 +387,12 @@ static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
> return ret;
> }
>
> +static int io_register_iowait(struct io_ring_ctx *ctx)
> +{
> + ctx->iowait_enabled = true;
> + return 0;
> +}
> +
> static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
> void __user *arg, unsigned nr_args)
> __releases(ctx->uring_lock)
> @@ -563,6 +569,12 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
> break;
> ret = io_unregister_napi(ctx, arg);
> break;
> + case IORING_REGISTER_IOWAIT:
> + ret = -EINVAL;
> + if (arg || nr_args)
> + break;
> + ret = io_register_iowait(ctx);
> + break;
This only allows you to set it, not clear it. I think we want to make it
pass in the value, and pass back the previous. Something ala:
static int io_register_iowait(struct io_ring_ctx *ctx, int val)
{
int was_enabled = ctx->iowait_enabled;
if (val)
ctx->iowait_enabled = 1;
else
ctx->iowait_enabled = 0;
return was_enabled;
}
and then:
case IORING_REGISTER_IOWAIT:
ret = -EINVAL;
if (arg)
break;
ret = io_register_iowait(ctx, nr_args);
break;
I'd also add a:
Fixes: 8a796565cec3 ("io_uring: Use io_schedule* in cqring wait")
and mark it for stable, so we at least attempt to make it something that
can be depended on.
--
Jens Axboe
