[Put Hugh back on CC] What happened to Hugh's fixes to the LRU handling? I believe it was racy beyond affecting memcg, it's just that memcg code had a BUG_ON in the right place to point it out. On Tue, Nov 13, 2012 at 06:13:44PM +0100, Ingo Molnar wrote: > From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > > Add THP migration for the NUMA working set scanning fault case. > > It uses the page lock to serialize. No migration pte dance is > necessary because the pte is already unmapped when we decide > to migrate. > > Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Mel Gorman <mgorman@xxxxxxx> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Link: http://lkml.kernel.org/n/tip-yv9vbiz2s455zxq1ffzx3fye@xxxxxxxxxxxxxx > [ Significant fixes and changelog. ] > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> > --- > mm/huge_memory.c | 131 +++++++++++++++++++++++++++++++++++++++++++------------ > mm/migrate.c | 2 +- > 2 files changed, 103 insertions(+), 30 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index c4c0a57..931caf4 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -742,12 +742,13 @@ void do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, > unsigned int flags, pmd_t entry) > { > unsigned long haddr = address & HPAGE_PMD_MASK; > + struct page *new_page = NULL; > struct page *page = NULL; > - int node; > + int node, lru; > > spin_lock(&mm->page_table_lock); > if (unlikely(!pmd_same(*pmd, entry))) > - goto out_unlock; > + goto unlock; > > if (unlikely(pmd_trans_splitting(entry))) { > spin_unlock(&mm->page_table_lock); > @@ -755,45 +756,117 @@ void do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, > return; > } > > -#ifdef CONFIG_NUMA > page = pmd_page(entry); > - VM_BUG_ON(!PageCompound(page) || !PageHead(page)); > + if (page) { > + VM_BUG_ON(!PageCompound(page) || !PageHead(page)); > > - get_page(page); > - spin_unlock(&mm->page_table_lock); > + get_page(page); > + node = mpol_misplaced(page, vma, haddr); > + if (node != -1) > + goto migrate; > + } > > - /* > - * XXX should we serialize against split_huge_page ? > - */ > +fixup: > + /* change back to regular protection */ > + entry = pmd_modify(entry, vma->vm_page_prot); > + set_pmd_at(mm, haddr, pmd, entry); > + update_mmu_cache_pmd(vma, address, entry); > > - node = mpol_misplaced(page, vma, haddr); > - if (node == -1) > - goto do_fixup; > +unlock: > + spin_unlock(&mm->page_table_lock); > + if (page) > + put_page(page); > > - /* > - * Due to lacking code to migrate thp pages, we'll split > - * (which preserves the special PROT_NONE) and re-take the > - * fault on the normal pages. > - */ > - split_huge_page(page); > - put_page(page); > return; > > -do_fixup: > +migrate: > + spin_unlock(&mm->page_table_lock); > + > + lock_page(page); > spin_lock(&mm->page_table_lock); > - if (unlikely(!pmd_same(*pmd, entry))) > - goto out_unlock; > -#endif > + if (unlikely(!pmd_same(*pmd, entry))) { > + spin_unlock(&mm->page_table_lock); > + unlock_page(page); > + put_page(page); > + return; > + } > + spin_unlock(&mm->page_table_lock); > > - /* change back to regular protection */ > - entry = pmd_modify(entry, vma->vm_page_prot); > - if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) > - update_mmu_cache_pmd(vma, address, entry); > + new_page = alloc_pages_node(node, > + (GFP_TRANSHUGE | GFP_THISNODE) & ~__GFP_WAIT, > + HPAGE_PMD_ORDER); > > -out_unlock: > + if (!new_page) > + goto alloc_fail; > + > + lru = PageLRU(page); > + > + if (lru && isolate_lru_page(page)) /* does an implicit get_page() */ > + goto alloc_fail; > + > + if (!trylock_page(new_page)) > + BUG(); > + > + /* anon mapping, we can simply copy page->mapping to the new page: */ > + new_page->mapping = page->mapping; > + new_page->index = page->index; > + > + migrate_page_copy(new_page, page); > + > + WARN_ON(PageLRU(new_page)); > + > + spin_lock(&mm->page_table_lock); > + if (unlikely(!pmd_same(*pmd, entry))) { > + spin_unlock(&mm->page_table_lock); > + if (lru) > + putback_lru_page(page); > + > + unlock_page(new_page); > + ClearPageActive(new_page); /* Set by migrate_page_copy() */ > + new_page->mapping = NULL; > + put_page(new_page); /* Free it */ > + > + unlock_page(page); > + put_page(page); /* Drop the local reference */ > + > + return; > + } > + > + entry = mk_pmd(new_page, vma->vm_page_prot); > + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); > + entry = pmd_mkhuge(entry); > + > + page_add_new_anon_rmap(new_page, vma, haddr); > + > + set_pmd_at(mm, haddr, pmd, entry); > + update_mmu_cache_pmd(vma, address, entry); > + page_remove_rmap(page); > spin_unlock(&mm->page_table_lock); > - if (page) > + > + put_page(page); /* Drop the rmap reference */ > + > + if (lru) > + put_page(page); /* drop the LRU isolation reference */ > + > + unlock_page(new_page); > + unlock_page(page); > + put_page(page); /* Drop the local reference */ > + > + return; > + > +alloc_fail: > + if (new_page) > + put_page(new_page); > + > + unlock_page(page); > + > + spin_lock(&mm->page_table_lock); > + if (unlikely(!pmd_same(*pmd, entry))) { > put_page(page); > + page = NULL; > + goto unlock; > + } > + goto fixup; > } > > int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, > diff --git a/mm/migrate.c b/mm/migrate.c > index 3299949..72d1056 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -417,7 +417,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping, > */ > void migrate_page_copy(struct page *newpage, struct page *page) > { > - if (PageHuge(page)) > + if (PageHuge(page) || PageTransHuge(page)) > copy_huge_page(newpage, page); > else > copy_highpage(newpage, page); > -- > 1.7.11.7 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>