this is intent to max lowmem_reserve.
in normal case,
shrink_active_list isn't called when free_pages > pages_high.
but just after memory freed, it happened rarely.
I don't want incorrect notify at system enough free memory.
related discussion
http://marc.info/?l=linux-mm&m=119878630211348&w=2
Nice idea.
I will applied it at next post.
thank you!
--