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    SubjectRe: [patch] smarter atime updates
    On Nov 30, 2001  13:44 -0200, Marcelo Tosatti wrote:
    > Now are you sure this can't break anything ?

    What fun would that be, if you couldn't follow in Linus' footsteps?
    People would get complacent if things didn't break now and again ;-).

    Anyways, you never want to put a change that is not a specific bug
    fix in a -rc patch anyways. Save it for a -pre patch, where you expect
    at least some testing before it is released.

    > On Thu, 29 Nov 2001, Andrew Morton wrote:
    > > mark_inode_dirty() is quite expensive for journalling filesystems,
    > > and we're calling it a lot more than we need to.
    > >
    > > --- linux-2.4.17-pre1/fs/inode.c Mon Nov 26 11:52:07 2001
    > > +++ linux-akpm/fs/inode.c Thu Nov 29 21:53:02 2001
    > > @@ -1187,6 +1187,8 @@ void __init inode_init(unsigned long mem
    > >
    > > void update_atime (struct inode *inode)
    > > {
    > > + if (inode->i_atime == CURRENT_TIME)
    > > + return;
    > > if ( IS_NOATIME (inode) ) return;
    > > if ( IS_NODIRATIME (inode) && S_ISDIR (inode->i_mode) ) return;
    > > if ( IS_RDONLY (inode) ) return;
    > >
    > >
    > > with this patch, the time to read a 10 meg file with 10 million
    > > read()s falls from 38 seconds (ext3), 39 seconds (reiserfs) and
    > > 11.6 seconds (ext2) down to 10.5 seconds.

    Well, just doing a code check of the update_atime() and UPDATE_ATIME()
    users, and they are all in readlink(), follow_link(), open_namei(),
    and various fs _readdir() codes. None of them (AFAICS) depend on the
    mark_inode_dirty() as a side-effect. This means it should be safe.

    Cheers, Andreas
    --
    Andreas Dilger
    http://sourceforge.net/projects/ext2resize/
    http://www-mddsp.enel.ucalgary.ca/People/adilger/

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