Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

From: Nick Piggin
Date: Fri Nov 04 2005 - 19:06:14 EST


Andi Kleen wrote:
On Friday 04 November 2005 22:31, Gregory Maxwell wrote:


Thats the idea. The 'hugetlb zone' will only be usable for allocations
which are guaranteed reclaimable. Reclaimable includes userspace
usage (since at worst an in use userspace page can be swapped out then
paged back into another physical location).


I don't like it very much. You have two choices if a workload runs
out of the kernel allocatable pages. Either you spill into the reclaimable
zone or you fail the allocation. The first means that the huge pages
thing is unreliable, the second would mean that all the many problems
of limited lowmem would be back.


These are essentially the same problems that the frag patches face as
well.

None of this is very attractive.


Though it is simple and I expect it should actually do a really good
job for the non-kernel-intensive HPC group, and the highly tuned
database group.

Nick

--
SUSE Labs, Novell Inc.

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