Re: Using swap though there's plenty of mem free

[Matthias Scheler <tron%zhadum.org.uk@localhost>]

On Thu, May 01, 2008 at 11:05:04PM +0200, Jonathan Schleifer wrote:
> Matthias Scheler <tron%zhadum.org.uk@localhost> wrote:
> 
> > What would be the sense in keeping allocated pages in memory even if
> > they haven't accessed for hours? Using the memory e.g. as disk
> > buffers will reduce the total amount of disk I/O which is what
> > a modern VM system tries to achieve.
> 
> That may be true for a desktop system, but NEVER for a server system.

It is true for any kind of system.

> If lighttpd is swapped because it wasn't used for some time, that's
> bad.

1.) I didn't talk about swapping out whole processes. I talked about
    pushing unused page to swap space.
2.) And if paging out bits of "lighthttpd" prevented gigabytes of
    unnecessary disk I/O it was the correct thing to do.

> On a desktop maybe, but not on a server. And as far as I know, NetBSD
> is used more for servers than for desktops, though it's a very nice
> system for a desktop as well.

No, it is not. It is not nice if unused processes block all the memory
and the I/O performance is bad. The VM system has of course to maintain
the correct ballance (and there might be situation where NetBSD's
doesn't do that).

        Kind regards

-- 
Matthias Scheler                                  http://zhadum.org.uk/