Messages in this thread | | | From | "Aneesh Kumar K.V" <> | Subject | Re: [PATCH 8/8] prepare to remove /proc/sys/vm/hugepages_treat_as_movable | Date | Thu, 01 Aug 2013 11:29:39 +0530 |
| |
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> writes:
> On Wed, Jul 31, 2013 at 12:02:30AM +0530, Aneesh Kumar K.V wrote: >> Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> writes: >> >> > Now hugepages are definitely movable. So allocating hugepages from >> > ZONE_MOVABLE is natural and we have no reason to keep this parameter. >> > In order to allow userspace to prepare for the removal, let's leave >> > this sysctl handler as noop for a while. >> >> I guess you still need to handle architectures for which pmd_huge is >> >> int pmd_huge(pmd_t pmd) >> { >> return 0; >> } >> >> embedded powerpc is one. They don't store pte information at the PMD >> level. Instead pmd contains a pointer to hugepage directory which >> contain huge pte. > > It seems that this comment is for the whole series, not just for this > patch, right? > > Some users of hugepage migration (mbind, move_pages, migrate_pages) > walk over page tables to collect hugepages to be migrated, where > hugepages are just ignored in such architectures due to pmd_huge. > So no problem for these users. > > But the other users (softoffline, memory hotremove) choose hugepages > to be migrated based on pfn, where they don't check pmd_huge. > As you wrote, this can be problematic for such architectures. > So I think of adding pmd_huge() check somewhere (in unmap_and_move_huge_page > for example) to make it fail for such architectures.
Considering that we have architectures that won't support migrating explicit hugepages with this patch series, is it ok to use GFP_HIGHUSER_MOVABLE for hugepage allocation ?
-aneesh
| |