From: Eric Sandeen <sandeen@redhat.com>
To: "Aneesh Kumar K. V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: paul.chavent@fnac.net, linux-ext4@vger.kernel.org
Subject: Re: What represent 646345728 bytes
Date: Mon, 01 Feb 2010 11:34:42 -0600 [thread overview]
Message-ID: <4B6710B2.9020701@redhat.com> (raw)
In-Reply-To: <871vh427qr.fsf@linux.vnet.ibm.com>
Aneesh Kumar K. V wrote:
> On Mon, 1 Feb 2010 15:08:24 +0100 (CET), <paul.chavent@fnac.net> wrote:
>> Hi
>>
>> I'am writing an application that write a stream of pictures of fixed size on a disk.
>>
>> My app run on a self integrated gnu/linux (based on a 2.6.31.6-rt19 kernel).
>>
>> My media is formated with
>>
>> # mke2fs -t ext4 -L DATA -O large_file,^has_journal,extent -v /dev/sda3
>> [...]
>>
>> And it is mounted with
>>
>> # mount -t ext4 /dev/sda3 /var/data/
>> EXT4-fs (sda3): no journal
>> EXT4-fs (sda3): delayed allocation enabled
>> EXT4-fs: file extents enabled
>> EXT4-fs: mballoc enabled
>> EXT4-fs (sda3): mounted filesystem without journal
>>
>> My app opens the file with "O_WRONLY | O_CREAT | O_TRUNC | O_SYNC | O_DIRECT" flags.
>>
>> Each write takes ~4.2ms for 304K (it is very good since it is the write bandwidth of my hard drive). There is a write every 100ms.
>>
>> But every exactly 646345728 bytes, the write takes ~46ms.
>
> I guess that would be balance_dirty_pages starting to writeback the
> delayed allocated pages. You can try if that changes by changing
> /proc/sys/vm/dirty_ratio
But he's doing direct IO...
-Eric
next prev parent reply other threads:[~2010-02-01 17:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-01 14:08 What represent 646345728 bytes paul.chavent
2010-02-01 15:06 ` Eric Sandeen
2010-02-01 17:20 ` Aneesh Kumar K. V
2010-02-01 17:34 ` Eric Sandeen [this message]
-- strict thread matches above, loose matches on Subject: below --
2010-02-01 17:06 paul.chavent
2010-02-01 20:07 ` Eric Sandeen
2010-02-01 22:36 ` Eric Sandeen
2010-02-01 23:01 ` Andreas Dilger
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