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

From: Joel Schopp
Date: Fri Feb 17 2006 - 16:30:30 EST


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.
http://sourceforge.net/mailarchive/message.php?msg_id=13864331




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