Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1768869Ab2KOT0N (ORCPT ); Thu, 15 Nov 2012 14:26:13 -0500 Received: from mga11.intel.com ([192.55.52.93]:21662 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1768856Ab2KOT0K (ORCPT ); Thu, 15 Nov 2012 14:26:10 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.83,259,1352102400"; d="scan'208";a="249687090" 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" , David Rientjes , "Kirill A. Shutemov" Subject: [PATCH v6 09/12] thp: lazy huge zero page allocation Date: Thu, 15 Nov 2012 21:26:59 +0200 Message-Id: <1353007622-18393-10-git-send-email-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1353007622-18393-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1353007622-18393-1-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 Content-Length: 2284 Lines: 84 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 file changed, 10 insertions(+), 10 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index ca3f6f2..bad9c8f 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -160,22 +160,24 @@ static int start_khugepaged(void) return err; } -static int __init 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) & ~__GFP_MOVABLE, 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) @@ -564,10 +566,6 @@ 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; @@ -590,8 +588,6 @@ 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; } @@ -728,6 +724,10 @@ 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; -- 1.7.11.7 -- 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/