Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932756AbbKDB1d (ORCPT ); Tue, 3 Nov 2015 20:27:33 -0500 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:41384 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030208AbbKDB0R (ORCPT ); Tue, 3 Nov 2015 20:26:17 -0500 X-Original-SENDERIP: 156.147.1.151 X-Original-MAILFROM: minchan@kernel.org X-Original-SENDERIP: 10.177.223.161 X-Original-MAILFROM: minchan@kernel.org From: Minchan Kim To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michael Kerrisk , linux-api@vger.kernel.org, Hugh Dickins , Johannes Weiner , Rik van Riel , Mel Gorman , KOSAKI Motohiro , Jason Evans , Daniel Micay , "Kirill A. Shutemov" , Shaohua Li , Michal Hocko , yalin.wang2010@gmail.com, Minchan Kim , Andrea Arcangeli Subject: [PATCH v2 13/13] mm: don't split THP page when syscall is called Date: Wed, 4 Nov 2015 10:26:07 +0900 Message-Id: <1446600367-7976-14-git-send-email-minchan@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1446600367-7976-1-git-send-email-minchan@kernel.org> References: <1446600367-7976-1-git-send-email-minchan@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5585 Lines: 178 We don't need to split THP page when MADV_FREE syscall is called. It could be done when VM decide to free it in reclaim path when memory pressure is heavy so we could avoid unnecessary THP split. For that, this patch changes two things 1. __split_huge_page_map It does pte_mkdirty to subpages only if pmd_dirty is true. 2. __split_huge_page_refcount It removes marking PG_dirty to subpages unconditionally. Cc: Kirill A. Shutemov Cc: Hugh Dickins Cc: Andrea Arcangeli Signed-off-by: Minchan Kim --- I don't understand why it added both SetPageDirty and pte_mkdirty to subpages unconditionally in split code of THP from the beginning. I guess at that time, there was no MADV_FREE so it was no problem and would be more safe to mark both but I might be missing something. Anyway, this patch doesn't have any problem so far for a few days of my test. I just added pmd_dirty respect code in split part of THP, not collapse intentionally because I don't see how it is helpful in real practice. Anyway, it could be done in future if it is needed, I think. include/linux/huge_mm.h | 3 +++ mm/huge_memory.c | 46 ++++++++++++++++++++++++++++++++++++++++++---- mm/madvise.c | 12 +++++++++++- 3 files changed, 56 insertions(+), 5 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index ecb080d6ff42..e9db238a75c1 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -19,6 +19,9 @@ extern struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd, unsigned int flags); +extern int madvise_free_huge_pmd(struct mmu_gather *tlb, + struct vm_area_struct *vma, + pmd_t *pmd, unsigned long addr); extern int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr); diff --git a/mm/huge_memory.c b/mm/huge_memory.c index bbac913f96bc..b8c9b44af864 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1453,6 +1453,41 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, return 0; } +int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, + pmd_t *pmd, unsigned long addr) + +{ + spinlock_t *ptl; + pmd_t orig_pmd; + struct page *page; + struct mm_struct *mm = tlb->mm; + + if (__pmd_trans_huge_lock(pmd, vma, &ptl) != 1) + return 1; + + orig_pmd = *pmd; + if (is_huge_zero_pmd(orig_pmd)) + goto out; + + page = pmd_page(orig_pmd); + if (PageActive(page)) + deactivate_page(page); + + if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { + orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, + tlb->fullmm); + orig_pmd = pmd_mkold(orig_pmd); + orig_pmd = pmd_mkclean(orig_pmd); + + set_pmd_at(mm, addr, pmd, orig_pmd); + tlb_remove_pmd_tlb_entry(tlb, pmd, addr); + } +out: + spin_unlock(ptl); + + return 0; +} + int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr) { @@ -1752,8 +1787,8 @@ static void __split_huge_page_refcount(struct page *page, (1L << PG_mlocked) | (1L << PG_uptodate) | (1L << PG_active) | - (1L << PG_unevictable))); - page_tail->flags |= (1L << PG_dirty); + (1L << PG_unevictable) | + (1L << PG_dirty))); /* clear PageTail before overwriting first_page */ smp_wmb(); @@ -1787,7 +1822,6 @@ static void __split_huge_page_refcount(struct page *page, BUG_ON(!PageAnon(page_tail)); BUG_ON(!PageUptodate(page_tail)); - BUG_ON(!PageDirty(page_tail)); BUG_ON(!PageSwapBacked(page_tail)); lru_add_page_tail(page, page_tail, lruvec, list); @@ -1831,10 +1865,12 @@ static int __split_huge_page_map(struct page *page, int ret = 0, i; pgtable_t pgtable; unsigned long haddr; + bool dirty; pmd = page_check_address_pmd(page, mm, address, PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl); if (pmd) { + dirty = pmd_dirty(*pmd); pgtable = pgtable_trans_huge_withdraw(mm, pmd); pmd_populate(mm, &_pmd, pgtable); if (pmd_write(*pmd)) @@ -1850,7 +1886,9 @@ static int __split_huge_page_map(struct page *page, * permissions across VMAs. */ entry = mk_pte(page + i, vma->vm_page_prot); - entry = maybe_mkwrite(pte_mkdirty(entry), vma); + if (dirty) + entry = pte_mkdirty(entry); + entry = maybe_mkwrite(entry, vma); if (!pmd_write(*pmd)) entry = pte_wrprotect(entry); if (!pmd_young(*pmd)) diff --git a/mm/madvise.c b/mm/madvise.c index 4e67ba0b1104..27ed057c0bd7 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -271,8 +271,17 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, pte_t *pte, ptent; struct page *page; int nr_swap = 0; + unsigned long next; + + next = pmd_addr_end(addr, end); + if (pmd_trans_huge(*pmd)) { + if (next - addr != HPAGE_PMD_SIZE) + split_huge_page_pmd(vma, addr, pmd); + else if (!madvise_free_huge_pmd(tlb, vma, pmd, addr)) + goto next; + /* fall through */ + } - split_huge_page_pmd(vma, addr, pmd); if (pmd_trans_unstable(pmd)) return 0; @@ -355,6 +364,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, arch_leave_lazy_mmu_mode(); pte_unmap_unlock(pte - 1, ptl); cond_resched(); +next: return 0; } -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/