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SubjectRe: Strange performance change 59 -> 61/62
"Martin J. Bligh" <mbligh@aracnet.com> wrote:
>
> > mark_inode_dirty() tends to be called _very_ frequently. Too frequently.
> >
> > Could you try remounting all filesystems noatime with
> >
> > mount /mnt/point -o remount,noatime
> >
> > and the below patch will prevent us calling the barrier-happy
> > current_kernel_time() for noatime mounts.
>
> Cool, that works nicely - thanks.
>
> 2.5.59-mjb6: 84 __mark_inode_dirty
> 2.5.61-mjb1: 594 __mark_inode_dirty
> 2.5.61-mjb1-no_mb: 74 __mark_inode_dirty
> 2.5.61-mjb1-noatime: 65 __mark_inode_dirty
>

OK. We used to only run mark_inode_dirty() for atime updates just when it
had actually changed. ie: once per second. But for reasons which remain
obscure that was taken out.

This probably explains your ext3 woes. Poor old ext3 has to do a ton of work
in ext3_mark_inode_dirty(), yet on 99% of the calls, nothing has even
changed. Which is why I suggested that you retest ext3 with noatime.

I shall fix it up.

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