Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

Linus Torvalds
2005-11-04T21:39:29Z

On Fri, 4 Nov 2005, Linus Torvalds wrote:
>
> But the hint can be pretty friendly. Especially if it's an option to just
> load a lot of memory into the boxes, and none of the loads are expected to
> want to really be excessively close to memory limits (ie you could just
> buy an extra 16GB to allow for "slop").

One of the issues _will_ be how to allocate things on NUMA. Right now
"hugetlb" only allows us to say "this much memory for hugetlb", and it
probably needs to be per-zone.

Some uses might want to allocate all of the local memory on one node to
huge-page usage (and specialized programs would then also like to run
pinned to that node), others migth want to spread it out. So the
maintenance would need to decide that.

The good news is that you can boot up with almost all zones being "big
page" zones, and you could turn them into "normal zones" dynamically. It's
only going the other way that is hard.

So from a maintenance standpoint if you manage lots of machines, you could
have them all uniformly boot up with lots of memory set aside for large
pages, and then use user-space tools to individually turn the zones into
regular allocation zones.

Linus