2010-06-10 12:44:28

by Yedire, Sandeep

[permalink] [raw]
Subject: O_NONBLOCK with Ext2/3

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

----------------------------------------------------------
T.Jefferson, 'Victory and defeat are each of the same price"


2010-06-11 00:50:21

by Robert Hancock

[permalink] [raw]
Subject: Re: O_NONBLOCK with Ext2/3

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.

2010-06-11 04:34:50

by Yedire, Sandeep

[permalink] [raw]
Subject: Re: O_NONBLOCK with Ext2/3

On 11 June 2010 06:20, Robert Hancock <[email protected]> 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