linux-kernel - Re: [PATCH RFC 1/2] fs/iomap/direct-io: pass NOWAIT to bio flags

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Message-ID: <94ec1b65-5f4c-6b56-5a47-ca186615d978@yandex-team.ru>
Date:   Mon, 4 May 2020 19:23:50 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH RFC 1/2] fs/iomap/direct-io: pass NOWAIT to bio flags

On 04/05/2020 19.00, Christoph Hellwig wrote:
> On Mon, May 04, 2020 at 06:54:53PM +0300, Konstantin Khlebnikov wrote:
>> This is required to avoid waiting in lower layers.
>>
>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> 
> This looks sensible.  Did you run this through xfstests?
> 

Nope. It seems xfstests has one trivial test for NOWAIT - generic/471
It tests only write with/without extent, nothing about contention.

I've added nowait into fio and played with it a little.
https://github.com/axboe/fio/pull/972

With these patches I see EAGAINs when queue is flooded.