linux-kernel - Re: Re: [PATCH v2] io_uring: Statistics of the true utilization of sq threads.

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Date:   Mon, 13 Nov 2023 11:10:40 +0800
From:   Xiaobing Li <xiaobing.li@...sung.com>
To:     axboe@...nel.dk
Cc:     asml.silence@...il.com, linux-kernel@...r.kernel.org,
        io-uring@...r.kernel.org, kun.dou@...sung.com,
        peiwei.li@...sung.com, joshi.k@...sung.com,
        kundan.kumar@...sung.com, wenwen.chen@...sung.com,
        ruyi.zhang@...sung.com, xiaobing.li@...sung.com
Subject: Re: Re: [PATCH v2] io_uring: Statistics of the true utilization of
 sq threads.

After careful consideration and testing, I don't think getting the
uring_lock is possible here, for the following reasons:
Due to lock competition, ctx->uring_lock and sq->lock are usually not
available here. The best proof is that the values of SqThread and
SqThreadCpu always output -1. In this case, it is impossible to obtain
the required work_time and total_time values.
In fact, it should be feasible to obtain work_time and total_time by
judging that ctx->sq_data is not NULL, because if the sq thread exits,
the action of reading data will also stop, and the possibility of a null
pointer reference is very low.