Messages in this thread |  | | Subject | Re: [PATCH] Hugepages should be accounted as unevictable pages. | From | Alok Kataria <> | Date | Tue, 23 Jun 2009 12:28:55 -0700 |
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On Mon, 2009-06-22 at 23:06 -0700, KAMEZAWA Hiroyuki wrote: > On Mon, 22 Jun 2009 22:54:01 -0700 > Alok Kataria <akataria@vmware.com> wrote: > > > > > > > > > I don't have any strong oppose reason, but I also don't have any strong > > > > agree reason. > > > > > > > I think "don't include Hugepage" is sane. Hugepage is something _special_, now. > > > > > Kamezawa-san, > > > > I agree that hugepages are special in the sense that they are > > implemented specially and don't actually reside on the LRU like any > > other locked memory. But, both of these memory types (mlocked and > > hugepages) are actually unevictable and can't be reclaimed back, so i > > don't see a reason why should accounting not reflect that. > > > > I bet we should rename "Unevictable" to "Mlocked" or "Pinned" rather than > take nr_hugepages into account. I think this "Unevictable" in meminfo means > - pages which are evictable in their nature (because in LRU) but a user pinned it - > > How about rename "Unevictable" to "Pinned" or "Locked" ? > (Mlocked + locked shmem's + ramfs?) >
As Lee also pointed out, i don't see why is this # of pages on unevictable_lru important for the user. IMO, it doesn't give any useful information, other than confusing us to believe that only these are unevictable.
Is there something else that I am missing here ?
> We have other "unevictable" pages other than Hugepage anyway. > - page table > - some slab > - kernel's page > - anon pages in swapless system > etc...
I agree there are these other pages which are unevictable, but they are pages used by the kernel itself, and they will always be locked/utilized by the kernel. The unevictable pages (hugepages and mlocked and others) on the other hand are pages which the user explicitly asked to be locked/pinned.
So i think, these other-evictable pages that you mentioned, are different in a way.
> > BTW, I use following calculation for quick check if I want all "Unevicatable" pages. > > Unevictable = Total - (Active+Inactive) + (50-70%? of slab) > > This # of is not-reclaimable memory.
I don't see how this would get the correct value either, mlocked or hugepages are not accounted by either of the Active or Inactive regions.
Thanks, Alok
> > Thanks, > -Kame > > > > Thanks, > > Alok > > > > > Thanks, > > > -Kame > > > > > > > >
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