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

[Glauber Costa]

On 11/30/2012 06:58 AM, Luck, Tony wrote:
>> 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.
> 

Which is a perfectly common workload for containers, where you can have
hundreds of machines (per node) being sold out to third parties, a lot
of them consuming every single bit of metadata they can.



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