Re: [PATCH RFC 5.13 1/2] io_uring: add support for ns granularity of io_sq_thread_idle

From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>,
	Hao Xu <haoxu@linux.alibaba.com>
Cc: io-uring@vger.kernel.org, Joseph Qi <joseph.qi@linux.alibaba.com>
Subject: Re: [PATCH RFC 5.13 1/2] io_uring: add support for ns granularity of io_sq_thread_idle
Date: Wed, 28 Apr 2021 08:16:07 -0600	[thread overview]
Message-ID: <2fadf565-beb3-4227-8fe7-3f9e308a14a0@kernel.dk> (raw)
In-Reply-To: <7136bf4f-089f-25d5-eaf8-1f55b946c005@gmail.com>

On 4/28/21 8:07 AM, Pavel Begunkov wrote:
>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
>> index e1ae46683301..311532ff6ce3 100644
>> --- a/include/uapi/linux/io_uring.h
>> +++ b/include/uapi/linux/io_uring.h
>> @@ -98,6 +98,7 @@ enum {
>>  #define IORING_SETUP_CLAMP	(1U << 4)	/* clamp SQ/CQ ring sizes */
>>  #define IORING_SETUP_ATTACH_WQ	(1U << 5)	/* attach to existing wq */
>>  #define IORING_SETUP_R_DISABLED	(1U << 6)	/* start with ring disabled */
>> +#define IORING_SETUP_IDLE_NS	(1U << 7)	/* unit of thread_idle is nano second */
>>  
>>  enum {
>>  	IORING_OP_NOP,
>> @@ -259,7 +260,7 @@ struct io_uring_params {
>>  	__u32 cq_entries;
>>  	__u32 flags;
>>  	__u32 sq_thread_cpu;
>> -	__u32 sq_thread_idle;
>> +	__u64 sq_thread_idle;
> 
> breaks userspace API

And I don't think we need to. If you're using IDLE_NS, then the value
should by definition be small enough that it'd fit in 32-bits. If you
need higher timeouts, don't set it and it's in usec instead.

So I'd just leave this one alone.

-- 
Jens Axboe