linux-ext4 - Re: how to disable readahead

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Message-ID: <077f573b5bba436e83875d2238760a18@SIWEX5A.sing.micron.com>
Date:   Thu, 2 Aug 2018 15:57:46 +0000
From:   "Bean Huo (beanhuo)" <beanhuo@...ron.com>
To:     Reindl Harald <h.reindl@...lounge.net>,
        Jack Wang <jack.wang.usish@...il.com>
CC:     "tytso@....edu" <tytso@....edu>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "beanhuo.linux@...gle.com" <beanhuo.linux@...gle.com>
Subject: Re: how to disable readahead

>>> I guess you're doing buffered IO, have you try to use direct IO?
>>>
>> Direct I/O is another case, it is true that will bypass readahead.
>> But I want to disable readahead with page cache.
>
>don't get me wrong but when you state "I am newbie on ext4" this all sounds
>like "having solution, seeking for problem"

No solution, I only want to disable ext4 readahead with keeping page cache.
I am curious about that flash based SDD/UFS/eMMC already has readahead in the FW, what is benefit of readahead in the FS under this condition?