> > 4. Performance test was done using the program available from the
> > following link:
> >
> >
http://bugzilla.kernel.org/attachment.cgi?id=14493
> >
> > Result: the impact of the changes was negligible for files of a few
> > hundred megabytes.
>
> Could you also test with ext4 and post some numbers? Afaik, ext4 uses
> nanosecond timestamps, so the time updating code would be exercised
> more during the page faults.
>
> What about performance impact on msync(MS_ASYNC)? Could you please do
> some measurment of that as well?