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Thu, 29 Apr 2021 02:12:00 -0700 (PDT) Subject: Re: [PATCH RFC 5.13 1/2] io_uring: add support for ns granularity of io_sq_thread_idle To: Hao Xu , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <1619616748-17149-1-git-send-email-haoxu@linux.alibaba.com> <1619616748-17149-2-git-send-email-haoxu@linux.alibaba.com> <7136bf4f-089f-25d5-eaf8-1f55b946c005@gmail.com> <2fadf565-beb3-4227-8fe7-3f9e308a14a0@kernel.dk> <3aa943b1-b53e-c3c5-7a45-278c2eebb861@linux.alibaba.com> From: Pavel Begunkov Message-ID: Date: Thu, 29 Apr 2021 10:11:55 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <3aa943b1-b53e-c3c5-7a45-278c2eebb861@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 4/29/21 4:41 AM, Hao Xu wrote: > 在 2021/4/28 下午10:16, Jens Axboe 写道: >> 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 > I make it u64 since I thought users may want a full flexibility to set > idle in nanosecond granularity(eg. (1e6 + 10) ns cannot be set by It's a really weird user requiring such a precision. u32 allows up to ~1s, and if more is needed users can switch to ms mode, so in the worst case the precision is 1/1000 of the desired value, more than enough. > millisecond granularity). But I'm not sure if this deserve changing the > userspace API. That's not about deserve or not, we can't break ABI. Can be worked around, e.g. by taking resv fields, but don't see a reason >> need higher timeouts, don't set it and it's in usec instead. >> >> So I'd just leave this one alone. >> > -- Pavel Begunkov