Re: [ckrm-tech] [PATCH 4/7] UBC: syscalls (user interface)

Chandra Seetharaman
2006-08-18T18:27:40Z

On Fri, 2006-08-18 at 11:17 -0700, Chandra Seetharaman wrote:
> On Fri, 2006-08-18 at 09:42 -0700, Andrew Morton wrote:
> > On Fri, 18 Aug 2006 07:45:48 -0700
> > Dave Hansen <haveblue@us.ibm.com> wrote:
> >
> > > On Fri, 2006-08-18 at 12:08 +0400, Andrey Savochkin wrote:
> > > >
> > > > A) Have separate memory management for each container,
> > > > with separate buddy allocator, lru lists, page replacement mechanism.
> > > > That implies a considerable overhead, and the main challenge there
> > > > is sharing of pages between these separate memory managers.
> > >
> > > Hold on here for just a sec...
> > >
> > > It is quite possible to do memory management aimed at one container
> > > while that container's memory still participates in the main VM.
> > >
> > > There is overhead here, as the LRU scanning mechanisms get less
> > > efficient, but I'd rather pay a penalty at LRU scanning time than divide
> > > up the VM, or coarsely start failing allocations.
> > >
> >
> > I have this mad idea that you can divide a 128GB machine up into 256 fake
> > NUMA nodes, then you use each "node" as a 512MB unit of memory allocation.
> > So that 4.5GB job would be placed within an exclusive cpuset which has nine
> > "mems" (what are these called?) and voila: the job has a hard 4.5GB limit,
> > no kernel changes needed.
>
> In this model memory and container are tightly coupled, hence memory
> might be unused/wasted in one container/resource group", while a
> different group is hitting its limit too often.
>
> In order to minimize this effect, resource controllers should be
> providing both minimum and maximum amount of resources available for a
> resource group.

Forgot to mention... There is a set of patches submitted by KUROSAWA
Takahiro that implements this by creating pseudo zones (It has the same
limitation though). http://marc.theaimsgroup.com/?l=ckrm-
tech&m=113867467006531&w=2

>
> >
> > Unfortunately this is not testable because numa=fake=256 doesn't come even
> > vaguely close to working. Am trying to get that fixed.
> >
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--

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Chandra Seetharaman | Be careful what you choose....
- sekharan@us.ibm.com | .......you may get it.
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