Messages in this thread | | | From | Scott Wood <> | Date | Mon, 05 Dec 2016 19:18:36 -0600 | Subject | Re: [PATCH v3 2/3] powerpc: get hugetlbpage handling more generic |
| |
On Wed, 2016-09-21 at 10:11 +0200, Christophe Leroy wrote: > Today there are two implementations of hugetlbpages which are managed > by exclusive #ifdefs: > * FSL_BOOKE: several directory entries points to the same single hugepage > * BOOK3S: one upper level directory entry points to a table of hugepages > > In preparation of implementation of hugepage support on the 8xx, we > need a mix of the two above solutions, because the 8xx needs both cases > depending on the size of pages: > * In 4k page size mode, each PGD entry covers a 4M bytes area. It means > that 2 PGD entries will be necessary to cover an 8M hugepage while a > single PGD entry will cover 8x 512k hugepages. > * In 16 page size mode, each PGD entry covers a 64M bytes area. It means > that 8x 8M hugepages will be covered by one PGD entry and 64x 512k > hugepages will be covers by one PGD entry. > > This patch: > * removes #ifdefs in favor of if/else based on the range sizes > * merges the two huge_pte_alloc() functions as they are pretty similar > * merges the two hugetlbpage_init() functions as they are pretty similar [snip] > @@ -860,16 +803,34 @@ static int __init hugetlbpage_init(void) > * if we have pdshift and shift value same, we don't > * use pgt cache for hugepd. > */ > - if (pdshift != shift) { > + if (pdshift > shift) { > pgtable_cache_add(pdshift - shift, NULL); > if (!PGT_CACHE(pdshift - shift)) > panic("hugetlbpage_init(): could not create > " > "pgtable cache for %d bit > pagesize\n", shift); > } > +#ifdef CONFIG_PPC_FSL_BOOK3E > + else if (!hugepte_cache) {
This else never triggers on book3e, because the way this function calculates pdshift is wrong for book3e (it uses PyD_SHIFT instead of HUGEPD_PxD_SHIFT). We later get OOMs because huge_pte_alloc() calculates pdshift correctly, tries to use hugepte_cache, and fails.
If the point of this patch is to remove the compile-time decision on whether to do things the book3e way, why are there still ifdefs such as the ones controlling the definition of HUGEPD_PxD_SHIFT? How does what you're doing on 8xx (for certain page sizes) differ from book3e?
-Scott
| |