Re: The performance and behaviour of the anti-fragmentation related patches

Joel Schopp
2007-03-02T16:31:51Z

>> Exhibiting a workload where the list patch breaks down and the zone
>> patch rescues it might help if it's felt that the combination isn't as
>> good as lists in isolation. I'm sure one can be dredged up somewhere.
>
> I can't think of a workload that totally makes a mess out of list-based.
> However, list-based makes no guarantees on availability. If a system
> administrator knows they need between 10,000 and 100,000 huge pages and
> doesn't want to waste memory pinning too many huge pages at boot-time,
> the zone-based mechanism would be what he wanted.

From our testing with earlier versions of list based for memory hot-unplug on
pSeries machines we were able to hot-unplug huge amounts of memory after running the
nastiest workloads we could find for over a week. Without the patches we were unable
to hot-unplug anything within minutes of running the same workloads.

If something works for 99.999% of people (list based) and there is an easy way to
configure it for the other 0.001% of the people ("zone" based) I call that a great
solution. I really don't understand what the resistance is to these patches.