Messages in this thread | | | Date | Sun, 28 Mar 2004 11:10:05 -0800 | From | "Martin J. Bligh" <> | Subject | Re: [PATCH] [0/6] HUGETLB memory commitment |
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> As I understood this originally, the suggestion was to reserve hugetlb > pages at mmap() or shm_get() time so that the user would get an -ENOMEM > at that time if there aren't enough hugetlb pages to (eventually) satisfy > the request, as per the notion that we shouldn't modify the user API due > to going with allocate on fault instead of hugetlb_prefault().
Yup, but there were two parts to it:
1. Stop hugepages using the existing overcommit pool for small pages, which breaks small page allocations by prematurely the pool. 2. Give hugepages their own over-commit pool, instead of prefaulting.
Personally I think we need both (as you seem to), but (1) is probably more urgent.
> Since the reservation belongs to the mapped object (file or segment), > I've been storing the current file/segments's reservation in the file > system dependent part of the inode. That way, it is easily accessible > when the hugetlbfs file or SysV segment is removed and we can reduce > the total number of reserved pages by that file's reservation at that > time. This also allows us to handle the reservation in the absence > of a vma, as per Andy'c comment below.
Do we need to store it there, or is one central pool number sufficient? I would have thought it was ...
> Admittedly this doesn't alow one to request that hugetlbpages be > overcommitted, or to handle problems caused to the "normal" page > overcommit code due to the presence of hugepages. But we figure that > anyone that is actually using hugetlb pages is likely to take over > almost all of main memory anyway in a single job, so overcommit > doesn't make much sense to us.
Seeing as you can't swap them, overcommitting makes no sense to me either ;-)
M.
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