Re: [RFC] [PATCH] Relative lazy atime
From: Frank van Maarseveen
Date: Thu Aug 10 2006 - 07:32:33 EST
On Wed, Aug 09, 2006 at 02:21:34PM +0200, Jörn Engel wrote:
> At the risk of stating the obvious, let me try to explain what each
> method does:
> 1. standard
> Every read access to a file/directory causes an atime update.
> 2. nodiratime
> Every read access to a non-directory causes an atime update.
> 3. lazy atime
> The first read access to a file/directory causes an atime update.
> 4. noatime
> No read access to a file/directory causes an atime update.
5. lazy atime writeout
To reduce the pain of a fully functional atime only flush "atime-dirty"
inodes when the on-disk/in-core atime difference becomes big enough
(e.g. by maintaining an "atime dirtyness" level for the in-core inode).
I haven't seen anyone mentioning it but properly written cleanup programs
for /tmp et.al. do depend on atimes. When a system crashes after a long
time then (3) and (4) will probably cause /tmp to be wiped out because
at the next boot all atimes will be really old.
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