Re: [PATCH -mm] vmscan: protect a fraction of file backed mapped pages from reclaim

Christoph Lameter
2009-05-14T20:29:18Z

On Wed, 13 May 2009, KOSAKI Motohiro wrote:

> > All these expiration modifications do not take into account that a desktop
> > may sit idle for hours while some other things run in the background (like
> > backups at night or updatedb and other maintenance things). This still
> > means that the desktop will be usuable in the morning.
>
> Have you seen this phenomenom?
> I always use linux desktop for development. but I haven't seen it.
> perhaps I have no luck. I really want to know reproduce way.
>
> Please let me know reproduce way.

Run a backup (or rsync) over a few hundred GB.

> > The percentage of file backed pages protected is set via
> > /proc/sys/vm/file_mapped_ratio. This defaults to 20%.
>
> Why do you think typical mapped ratio is less than 20% on desktop machine?

Observation of the typical mapped size of Firefox under KDE.

> key point is access-once vs access-many.

Nothing against it if it works.