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Message-ID: <871vh427qr.fsf@linux.vnet.ibm.com> Date: Mon, 01 Feb 2010 22:50:12 +0530 From: "Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com> To: paul.chavent@...c.net, linux-ext4@...r.kernel.org Subject: Re: What represent 646345728 bytes On Mon, 1 Feb 2010 15:08:24 +0100 (CET), <paul.chavent@...c.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 -aneesh -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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