From 12724850e8064f64b6223d26d78c0597c742c65a Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Wed, 21 Mar 2012 16:34:28 -0700 Subject: [PATCH] memcg: avoid THP split in task migration Currently we can't do task migration among memory cgroups without THP split, which means processes heavily using THP experience large overhead in task migration. This patch introduces the code for moving charge of THP and makes THP more valuable. Signed-off-by: Naoya Horiguchi Acked-by: Hillf Danton Cc: Andrea Arcangeli Acked-by: KAMEZAWA Hiroyuki Cc: David Rientjes Cc: Daisuke Nishimura Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 85 ++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 77 insertions(+), 8 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c8d00a9780bc..b2ee6df0e9bb 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5256,6 +5256,41 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma, return ret; } +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +/* + * We don't consider swapping or file mapped pages because THP does not + * support them for now. + * Caller should make sure that pmd_trans_huge(pmd) is true. + */ +static enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma, + unsigned long addr, pmd_t pmd, union mc_target *target) +{ + struct page *page = NULL; + struct page_cgroup *pc; + enum mc_target_type ret = MC_TARGET_NONE; + + page = pmd_page(pmd); + VM_BUG_ON(!page || !PageHead(page)); + if (!move_anon()) + return ret; + pc = lookup_page_cgroup(page); + if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) { + ret = MC_TARGET_PAGE; + if (target) { + get_page(page); + target->page = page; + } + } + return ret; +} +#else +static inline enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma, + unsigned long addr, pmd_t pmd, union mc_target *target) +{ + return MC_TARGET_NONE; +} +#endif + static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct mm_walk *walk) @@ -5264,9 +5299,12 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd, pte_t *pte; spinlock_t *ptl; - split_huge_page_pmd(walk->mm, pmd); - if (pmd_trans_unstable(pmd)) + if (pmd_trans_huge_lock(pmd, vma) == 1) { + if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE) + mc.precharge += HPAGE_PMD_NR; + spin_unlock(&vma->vm_mm->page_table_lock); return 0; + } pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) @@ -5425,18 +5463,49 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd, struct vm_area_struct *vma = walk->private; pte_t *pte; spinlock_t *ptl; + enum mc_target_type target_type; + union mc_target target; + struct page *page; + struct page_cgroup *pc; - split_huge_page_pmd(walk->mm, pmd); - if (pmd_trans_unstable(pmd)) + /* + * We don't take compound_lock() here but no race with splitting thp + * happens because: + * - if pmd_trans_huge_lock() returns 1, the relevant thp is not + * under splitting, which means there's no concurrent thp split, + * - if another thread runs into split_huge_page() just after we + * entered this if-block, the thread must wait for page table lock + * to be unlocked in __split_huge_page_splitting(), where the main + * part of thp split is not executed yet. + */ + if (pmd_trans_huge_lock(pmd, vma) == 1) { + if (!mc.precharge) { + spin_unlock(&vma->vm_mm->page_table_lock); + return 0; + } + target_type = get_mctgt_type_thp(vma, addr, *pmd, &target); + if (target_type == MC_TARGET_PAGE) { + page = target.page; + if (!isolate_lru_page(page)) { + pc = lookup_page_cgroup(page); + if (!mem_cgroup_move_account(page, HPAGE_PMD_NR, + pc, mc.from, mc.to, + false)) { + mc.precharge -= HPAGE_PMD_NR; + mc.moved_charge += HPAGE_PMD_NR; + } + putback_lru_page(page); + } + put_page(page); + } + spin_unlock(&vma->vm_mm->page_table_lock); return 0; + } + retry: pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); for (; addr != end; addr += PAGE_SIZE) { pte_t ptent = *(pte++); - union mc_target target; - int type; - struct page *page; - struct page_cgroup *pc; swp_entry_t ent; if (!mc.precharge) -- 2.20.1