Re: [RFC][PATCH 0/8] Critical Page Pool

Pavel Machek
2005-12-10T08:39:15Z

Hi!

> > ...and then you find out that your test was not "bad enough" or that
> > it needs more memory on different machines. It may be good enough hack
> > for your usage, but I do not think it belongs in mainline.
> > Pavel
>
> Way late in responding to this, but...
>
> Apropriate sizing of this pool is a known issue. For example, we want to
> use it to keep the networking stack alive during extreme memory pressure
> situations. The only way to size the pool so as to *guarantee* that it
> will not be exhausted during the 2 minute window we need would be to ensure
> that the pool has at least (TOTAL_BANDWITH_OF_ALL_NICS * 120 seconds) bytes
> available. In the case of a simple system with a single GigE adapter we'd
> need (1 gigbit/sec * 120 sec) = 120 gigabits = 15 gigabytes of reserve
> pool. That is obviously completely impractical, considering many boxes

And it is not enough... If someone hits you with small packets,
allocation overhead is going to be high.
Pavel
--
Thanks, Sharp!