Hi Tony,

2012/11/29 6:34, Luck, Tony wrote:

quoted

1. use firmware information
   According to ACPI spec 5.0, SRAT table has memory affinity structure
   and the structure has Hot Pluggable Filed. See "5.2.16.2 Memory
   Affinity Structure". If we use the information, we might be able to
   specify movable memory by firmware. For example, if Hot Pluggable
   Filed is enabled, Linux sets the memory as movable memory.

2. use boot option
   This is our proposal. New boot option can specify memory range to use
   as movable memory.

Isn't this just moving the work to the user? To pick good values for the

Yes.

movable areas, they need to know how the memory lines up across
node boundaries ... because they need to make sure to allow some
non-movable memory allocations on each node so that the kernel can
take advantage of node locality.

There is no problem.
Linux has already two boot options, kernelcore= and movablecore=.
So if we use them, non-movable memory is divided into each node evenly.

But there is no way to specify a node used as movable currently. So
we proposed the new boot option.

So the user would have to read at least the SRAT table, and perhaps
more, to figure out what to provide as arguments.

Since this is going to be used on a dynamic system where nodes might
be added an removed - the right values for these arguments might
change from one boot to the next. So even if the user gets them right
on day 1, a month later when a new node has been added, or a broken
node removed the values would be stale.

I don't think so. Even if we hot add/remove node, the memory range of
each memory device is not changed. So we don't need to change the boot
option.

Thanks,
Yasuaki Ishimatsu

-Tony

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