Re: [PATCH 4/7] ppc64 - Specify amount of kernel memory at boot time

Joel Schopp
2006-02-17T21:32:36Z

>> This patch adds the kernelcore= parameter for ppc64.
>>
>> The amount of memory will requested will not be reserved in all nodes. The
>> first node that is found that can accomodate the requested amount of memory
>> and have remaining more for ZONE_EASYRCLM is used. If a node has memory holes,
>> it also will not be used.
>
> One thing I think we really need to see before these go into mainline is
> the ability to shrink the ZONE_EASYRCLM at runtime, and give the memory
> back to NORMAL/DMA.
>
> Otherwise, any system starting off sufficiently small will end up having
> lowmem starvation issues. Allowing resizing at least gives the admin a
> chance to avoid those issues.
>

I'm not too keen on calling it resizing, because that term is
misleading. The resizing is one way. You can't later resize back. It's
like a window that you can only close but never reopen. We should call
it "runtime incremental disabling", or RID.

I don't think we need RID in order to merge these patches. RID can be
merged later if people decide they want a special easy reclaim zone that
could disappear at any moment. I personally fall in the camp of wanting
my zones I explicitly enabled to stay put and am opposed to RID.

If only somebody had presented a solution that was flexible enough to
dynamically resize reclaimable and non-reclaimable both ways.