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

KAMEZAWA Hiroyuki
2007-03-02T03:43:06Z

On Thu, 1 Mar 2007 16:09:15 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Thu, 1 Mar 2007 10:12:50 +0000
> mel@skynet.ie (Mel Gorman) wrote:
>
> > Any opinion on merging these patches into -mm
> > for wider testing?
>
> I'm a little reluctant to make changes to -mm's core mm unless those
> changes are reasonably certain to be on track for mainline, so let's talk
> about that.
>
> What worries me is memory hot-unplug and per-container RSS limits. We
> don't know how we're going to do either of these yet, and it could well be
> that the anti-frag work significantly complexicates whatever we end up
> doing there.
>
> For prioritisation purposes I'd judge that memory hot-unplug is of similar
> value to the antifrag work (because memory hot-unplug permits DIMM
> poweroff).

About memory-hot-unplug, I'm now writing a new patch-set for memory-unplug for
showing my overview and roadmap. I'm now debugging it. I think I will be able to
post them as RFC in a week.

At least, ZONE_MOVABLE(or something partitioning memory) is necessary for
memory-hot-unplug like DIMM-poweroff. (I'm now using my own ZONE_MOVABLE patch, but
It is O.K. to migrate to Mel's one if it's ready to be merged.)

> Our basic unit of memory management is the zone. Right now, a zone maps
> onto some hardware-imposed thing. But the zone-based MM works *well*. I
> suspect that a good way to solve both per-container RSS and mem hotunplug
> is to split the zone concept away from its hardware limitations: create a
> "software zone" and a "hardware zone". All the existing page allocator and
> reclaim code remains basically unchanged, and it operates on "software
> zones". Each software zones always lies within a single hardware zone.
> The software zones are resizeable. For per-container RSS we give each
> container one (or perhaps multiple) resizeable software zones.
>
> For memory hotunplug, some of the hardware zone's software zones are marked
> reclaimable and some are not; DIMMs which are wholly within reclaimable
> zones can be depopulated and powered off or removed.
>
Hmm...software-zone seems attractive.
I remember someone posted pesuedo-zone(pzone) patch in past.

-Kame