RE: [PATCH v2 0/5] Add movablecore_map boot option

From: Luck, Tony
Date: Thu Nov 29 2012 - 21:59:04 EST


> If any significant percentage of memory is in ZONE_MOVABLE then the memory
> hotplug people will have to deal with all the lowmem/highmem problems
> that used to be faced by 32-bit x86 with PAE enabled.

While these problems may still exist on large systems - I think it becomes
harder to construct workloads that run into problems. In those bad old days
a significant fraction of lowmem was consumed by the kernel ... so it was
pretty easy to find meta-data intensive workloads that would push it over
a cliff. Here we are talking about systems with say 128GB per node divided
into 64GB moveable and 64GB non-moveable (and I'd regard this as a rather
low-end machine). Unless the workload consists of zillions of tiny processes
all mapping shared memory blocks, the percentage of memory allocated to
the kernel is going to be tiny compared with the old 4GB days.

-Tony

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