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Date: Mon, 01 Feb 2010 11:34:42 -0600 From: Eric Sandeen <sandeen@...hat.com> To: "Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com> CC: paul.chavent@...c.net, linux-ext4@...r.kernel.org Subject: Re: What represent 646345728 bytes Aneesh Kumar K. V wrote: > 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 But he's doing direct IO... -Eric -- 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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