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From:   Pavel Begunkov <asml.silence@gmail.com>
To:     Ingo Molnar <mingo@kernel.org>, Jens Axboe <axboe@kernel.dk>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
References: <cover.1569139018.git.asml.silence@gmail.com>
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Subject: Re: [PATCH v2 0/2] Optimise io_uring completion waiting
Message-ID: <df612e90-8999-0085-d2d6-4418e044e429@gmail.com>
Date:   Mon, 23 Sep 2019 19:32:34 +0300
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From: Pavel Begunkov <asml.silence@gmail.com>
To: Ingo Molnar <mingo@kernel.org>, Jens Axboe <axboe@kernel.dk>
Cc: Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
 linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Message-ID: <df612e90-8999-0085-d2d6-4418e044e429@gmail.com>
Subject: Re: [PATCH v2 0/2] Optimise io_uring completion waiting
References: <cover.1569139018.git.asml.silence@gmail.com>
 <a4996ae7-ac0a-447b-49b2-7e96275aad29@kernel.dk>
 <20190923083549.GA42487@gmail.com>
 <c15b2d54-c722-8fb4-266f-b589c1a21aa5@gmail.com>
In-Reply-To: <c15b2d54-c722-8fb4-266f-b589c1a21aa5@gmail.com>

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Sorry, mixed the threads.

>>
>> I'm not sure an extension is needed for such a special interface, why =
not=20
>> just put a ->threshold value next to the ctx->wait field and use eithe=
r=20
>> the regular wait_event() APIs with the proper condition, or=20
>> wait_event_cmd() style APIs if you absolutely need something more comp=
lex=20
>> to happen inside?
Ingo,
io_uring works well without this patch just using wait_event_*() with
proper condition, but there are performance issues with spurious
wakeups. Detailed description in the previous mail.
Am I missing something?
Thanks


>>
>> Should result in a much lower linecount and no scheduler changes. :-)
>>
>> Thanks,
>>
>> 	Ingo
>>
>=20

--=20
Yours sincerely,
Pavel Begunkov


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