[erlang-questions] Linux O_DIRECT flag

[Alpár Jüttner]

On Fri, 2008-03-14 at 20:53 -0400, Toby Thain wrote:
> 
> On 14-Mar-08, at 5:14 PM, Valentin Micic wrote:
> 
> > Not when your application starts to swap-in and out because it is
> > running out of RAM, 

> That should never happen!

It may be, but it still happens. For example if you just copy a very big
file of directory tree (cp -a), the linux desktop often becomes unusably
sluggish. If you don't use an application (e.g. Firefox) for some time,
it gets out of the RAM and it takes several seconds until it reacts the
first click. Some time later you want to go back to Emacs, the same
happens.

But this should be a factor of the kernel configuration, because
sometimes linux does it sometime it doesn't. For example there is a
kernel 'swappisess' parameter /proc/sys/vm/swappiness which should
control this. I asked google about this file and the first hit was this:

http://lwn.net/Articles/83588/

Regards,
Alpar