linux-kernel - Re: O_NONBLOCK with Ext2/3

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Message-ID: <AANLkTilm0X3Uckl1S926hSPYRxh7jDeUm0WITOqac9V1@mail.gmail.com>
Date:	Fri, 11 Jun 2010 10:04:46 +0530
From:	"Yedire, Sandeep" <syedire@...il.com>
To:	Robert Hancock <hancockrwd@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: O_NONBLOCK with Ext2/3

On 11 June 2010 06:20, Robert Hancock <hancockrwd@...il.com> wrote:
> On 06/10/2010 06:44 AM, Yedire, Sandeep wrote:
>>
>> Hi All,
>> What is the effect  on filesystem blocks,data blocks if O_NONBLOCK
>> flag is used with a test application doing write to a file(64MB) on
>> NAND Flash.
>> Can any one please let me know
>> Regards,
>> Sandeep.Yedire
>
> O_NONBLOCK doesn't do anything on regular files, as far as I'm aware. It's
> only useful on sockets, serial ports/TTYs, etc.
>

[Sandeep] In Ext2 fs, I have noticed many frequent updates to data
blocks as compared to without this flag. I also noticed Dirty page
limit (44MB max)  with O_NONBLOCK and 18 to 20MB max without this
flag. Because of this there is less Filesystem block updates with
O_NONBLOCK flag.

In case of Ext3, Dirty page limit is 18-20MB with or without this flag.
Its same with all modes of Ext3(data, ordered, writeback).

This is actually my concern.

Many Thanks,
Sandeep
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