On Thu, 21 Jun 2012, David Rientjes wrote:

It's possible that subsequent pageblocks would contain memory allocated 
from solely non-oom memcgs, but it's certainly not a guarantee and results 
in terrible performance as exhibited above.  Is there another good 
criteria to use when deciding when to stop isolating and attempting to 
migrate all of these pageblocks?

Other ideas?

The only other alternative that I can think of is to check 
mem_cgroup_margin() in isolate_migratepages_range() and return a NULL 
lruvec that would break that pageblock and return, and then set a bit in 
struct mem_cgroup that labels it as oom so we can check for it on 
subsequent pageblocks without incurring the locking to do 
mem_cgroup_margin() in res_counter, and then clear that bit on every 
uncharge to a memcg, but this still seems like a tremendous waste of cpu 
(especially if /sys/kernel/mm/transparent_hugepage/defrag == always) if 
most pageblocks contain pages from an oom memcg.

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