From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756926Ab2IJNOw (ORCPT ); Mon, 10 Sep 2012 09:14:52 -0400 Received: from mga11.intel.com ([192.55.52.93]:53908 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750718Ab2IJNNY (ORCPT ); Mon, 10 Sep 2012 09:13:24 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.80,398,1344236400"; d="scan'208";a="220245346" From: "Kirill A. Shutemov" To: Andrew Morton , Andrea Arcangeli , linux-mm@kvack.org Cc: Andi Kleen , "H. Peter Anvin" , linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , "Kirill A. Shutemov" Subject: [PATCH v2 09/10] thp: lazy huge zero page allocation Date: Mon, 10 Sep 2012 16:13:32 +0300 Message-Id: <1347282813-21935-10-git-send-email-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1347282813-21935-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1347282813-21935-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Kirill A. Shutemov" Instead of allocating huge zero page on hugepage_init() we can postpone it until first huge zero page map. It saves memory if THP is not in use. cmpxchg() is used to avoid race on huge_zero_pfn initialization. Signed-off-by: Kirill A. Shutemov --- mm/huge_memory.c | 20 ++++++++++---------- 1 files changed, 10 insertions(+), 10 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index c788445..0981b09 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -168,21 +168,23 @@ out: return err; } -static int init_huge_zero_page(void) +static int init_huge_zero_pfn(void) { struct page *hpage; + unsigned long pfn; hpage = alloc_pages(GFP_TRANSHUGE | __GFP_ZERO, HPAGE_PMD_ORDER); if (!hpage) return -ENOMEM; - - huge_zero_pfn = page_to_pfn(hpage); + pfn = page_to_pfn(hpage); + if (cmpxchg(&huge_zero_pfn, 0, pfn)) + __free_page(hpage); return 0; } static inline bool is_huge_zero_pfn(unsigned long pfn) { - return pfn == huge_zero_pfn; + return huge_zero_pfn && pfn == huge_zero_pfn; } static inline bool is_huge_zero_pmd(pmd_t pmd) @@ -573,10 +575,6 @@ static int __init hugepage_init(void) if (err) return err; - err = init_huge_zero_page(); - if (err) - goto out; - err = khugepaged_slab_init(); if (err) goto out; @@ -601,8 +599,6 @@ static int __init hugepage_init(void) return 0; out: - if (huge_zero_pfn) - __free_page(pfn_to_page(huge_zero_pfn)); hugepage_exit_sysfs(hugepage_kobj); return err; } @@ -752,6 +748,10 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, return VM_FAULT_OOM; if (!(flags & FAULT_FLAG_WRITE)) { pgtable_t pgtable; + if (unlikely(!huge_zero_pfn && init_huge_zero_pfn())) { + count_vm_event(THP_FAULT_FALLBACK); + goto out; + } pgtable = pte_alloc_one(mm, haddr); if (unlikely(!pgtable)) goto out; -- 1.7.7.6