Messages in this thread | | | Date | Sun, 14 Mar 2004 15:06:34 +1100 | From | Anton Blanchard <> | Subject | Re: [Lse-tech] Re: Hugetlbpages in very large memory machines....... |
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> Demand-paging the hugepages is a decent feature to have, and ISTR resisting > it before for this reason. > > Even though it's early in the 2.6 series I'd be a bit worried about > breaking existing hugetlb users in this way. Yes, the pages are > preallocated so it is unlikely that a working setup is suddenly going to > break. Unless someone is using the return value from mmap to find out how > many pages they can get.
Hmm what a coincidence, I was chasing a problem where large page allocations would fail even though I clearly had enough large page memory free.
It turns out we were tripping the overcommit logic in do_mmap. I had 30GB of large page and 2GB of small pages and of course cap_vm_enough_memory was looking at the small page pool. Setting overcommit to 1 fixed it.
It seems we can solve both problems by having a separate hugetlb overcommit policy. Make it strict and you wont have OOM problems on large pages and I wont hit my 30GB / 2GB problem.
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