On Thu, Nov 29, 2012 at 07:38:26PM +0900, Yasuaki Ishimatsu wrote:

Hi Tony,

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

quoted

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.

quoted

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.

The motivation for those options was to reserve a percentage of memory
to be used for hugepage allocation. If hugepages were not being used at
a particular time then they could be used for other purposes. While the
system could in theory face lowmem/highmem style problems, in practice
it did not happen because the memory would be allocated as hugetlbfs
pages and unavailable anyway. The same does not really apply to a general
purpose system that you want to support memory hot-remove on so be wary of
lowmem/highmem style problems caused by relying too heavily on ZONE_MOVABLE.

-- 
Mel Gorman
SUSE Labs

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>