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Linux: Replacing atime With relatime

Aug 09, 2007, 12:00 (2 Talkback[s])

"In a recent lkml thread, Linus Torvalds was involved in a discussion about mounting filesystems with the noatime option for better performance, ''noatime,data=writeback' will quite likely be *quite* noticeable (with different effects for different loads), but almost nobody actually runs that way.' He noted that he set O_NOATIME when writing git, 'and it was an absolutely huge time-saver for the case of not having 'noatime' in the mount options. Certainly more than your estimated 10% under some loads.' The discussion then looked at using the relatime mount option to improve the situation, 'relative atime only updates the atime if the previous atime is older than the mtime or ctime. Like noatime, but useful for applications like mutt that need to know when a file has been read since it was last modified.' Ingo Molnar stressed the significance of fixing this performance issue, 'I cannot over-emphasize how much of a deal it is in practice. Atime updates are by far the biggest IO performance deficiency that Linux has today. Getting rid of atime updates would give us more everyday Linux performance than all the pagecache speedups of the past 10 years, _combined_.' He submitted some patches to improve relatime, and noted about atime..."

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