linux-kernel - Re: [PATCH 3/3] IO_URING: Statistics of the true utilization of sq threads.

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Message-ID: <ZRU7UzMlx6lpuEHG@casper.infradead.org>
Date:   Thu, 28 Sep 2023 09:37:39 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Xiaobing Li <xiaobing.li@...sung.com>, mingo@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        axboe@...nel.dk, asml.silence@...il.com,
        linux-kernel@...r.kernel.org, linux-fsdevel@...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
Subject: Re: [PATCH 3/3] IO_URING: Statistics of the true utilization of sq
 threads.

On Thu, Sep 28, 2023 at 10:01:14AM +0200, Peter Zijlstra wrote:
> Now, I see what you're trying to do, but who actually uses this data?

I ... don't.  There seems to be the notion that since we're polling, that
shouldn't count against the runtime of the thread.  But the thread has
chosen to poll!  It is doing something!  For one thing, it's preventing
the CPU from entering an idle state.  It seems absolutely fair to
accuont this poll time to the runtime of the thread.  Clearly i'm
missing something.