From: riel@redhat.com To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-mm@kvack.org, peterz@infradead.org, chegu_vinod@hp.com, aarcange@redhat.com, akpm@linux-foundation.org Subject: [PATCH -mm 3/3] move mmu notifier call from change_protection to change_pmd_range Date: Tue, 18 Feb 2014 17:12:46 -0500 [thread overview] Message-ID: <1392761566-24834-4-git-send-email-riel@redhat.com> (raw) In-Reply-To: <1392761566-24834-1-git-send-email-riel@redhat.com> From: Rik van Riel <riel@redhat.com> The NUMA scanning code can end up iterating over many gigabytes of unpopulated memory, especially in the case of a freshly started KVM guest with lots of memory. This results in the mmu notifier code being called even when there are no mapped pages in a virtual address range. The amount of time wasted can be enough to trigger soft lockup warnings with very large KVM guests. This patch moves the mmu notifier call to the pmd level, which represents 1GB areas of memory on x86-64. Furthermore, the mmu notifier code is only called from the address in the PMD where present mappings are first encountered. The hugetlbfs code is left alone for now; hugetlb mappings are not relocatable, and as such are left alone by the NUMA code, and should never trigger this problem to begin with. Signed-off-by: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Reported-by: Xing Gang <gang.xing@hp.com> Tested-by: Chegu Vinod <chegu_vinod@hp.com> --- mm/mprotect.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/mm/mprotect.c b/mm/mprotect.c index 6006c05..44850ee 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -109,9 +109,11 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pgprot_t newprot, int dirty_accountable, int prot_numa) { pmd_t *pmd; + struct mm_struct *mm = vma->vm_mm; unsigned long next; unsigned long pages = 0; unsigned long nr_huge_updates = 0; + unsigned long mni_start = 0; pmd = pmd_offset(pud, addr); do { @@ -120,6 +122,13 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, next = pmd_addr_end(addr, end); if (!pmd_trans_huge(*pmd) && pmd_none_or_clear_bad(pmd)) continue; + + /* invoke the mmu notifier if the pmd is populated */ + if (!mni_start) { + mni_start = addr; + mmu_notifier_invalidate_range_start(mm, mni_start, end); + } + if (pmd_trans_huge(*pmd)) { if (next - addr != HPAGE_PMD_SIZE) split_huge_page_pmd(vma, addr, pmd); @@ -143,6 +152,9 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pages += this_pages; } while (pmd++, addr = next, addr != end); + if (mni_start) + mmu_notifier_invalidate_range_end(mm, mni_start, end); + if (nr_huge_updates) count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); return pages; @@ -205,12 +217,12 @@ unsigned long change_protection(struct vm_area_struct *vma, unsigned long start, struct mm_struct *mm = vma->vm_mm; unsigned long pages; - mmu_notifier_invalidate_range_start(mm, start, end); - if (is_vm_hugetlb_page(vma)) + if (is_vm_hugetlb_page(vma)) { + mmu_notifier_invalidate_range_start(mm, start, end); pages = hugetlb_change_protection(vma, start, end, newprot); - else + mmu_notifier_invalidate_range_end(mm, start, end); + } else pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa); - mmu_notifier_invalidate_range_end(mm, start, end); return pages; } -- 1.8.5.3
WARNING: multiple messages have this Message-ID (diff)
From: riel@redhat.com To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-mm@kvack.org, peterz@infradead.org, chegu_vinod@hp.com, aarcange@redhat.com, akpm@linux-foundation.org Subject: [PATCH -mm 3/3] move mmu notifier call from change_protection to change_pmd_range Date: Tue, 18 Feb 2014 17:12:46 -0500 [thread overview] Message-ID: <1392761566-24834-4-git-send-email-riel@redhat.com> (raw) In-Reply-To: <1392761566-24834-1-git-send-email-riel@redhat.com> From: Rik van Riel <riel@redhat.com> The NUMA scanning code can end up iterating over many gigabytes of unpopulated memory, especially in the case of a freshly started KVM guest with lots of memory. This results in the mmu notifier code being called even when there are no mapped pages in a virtual address range. The amount of time wasted can be enough to trigger soft lockup warnings with very large KVM guests. This patch moves the mmu notifier call to the pmd level, which represents 1GB areas of memory on x86-64. Furthermore, the mmu notifier code is only called from the address in the PMD where present mappings are first encountered. The hugetlbfs code is left alone for now; hugetlb mappings are not relocatable, and as such are left alone by the NUMA code, and should never trigger this problem to begin with. Signed-off-by: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Reported-by: Xing Gang <gang.xing@hp.com> Tested-by: Chegu Vinod <chegu_vinod@hp.com> --- mm/mprotect.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/mm/mprotect.c b/mm/mprotect.c index 6006c05..44850ee 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -109,9 +109,11 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pgprot_t newprot, int dirty_accountable, int prot_numa) { pmd_t *pmd; + struct mm_struct *mm = vma->vm_mm; unsigned long next; unsigned long pages = 0; unsigned long nr_huge_updates = 0; + unsigned long mni_start = 0; pmd = pmd_offset(pud, addr); do { @@ -120,6 +122,13 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, next = pmd_addr_end(addr, end); if (!pmd_trans_huge(*pmd) && pmd_none_or_clear_bad(pmd)) continue; + + /* invoke the mmu notifier if the pmd is populated */ + if (!mni_start) { + mni_start = addr; + mmu_notifier_invalidate_range_start(mm, mni_start, end); + } + if (pmd_trans_huge(*pmd)) { if (next - addr != HPAGE_PMD_SIZE) split_huge_page_pmd(vma, addr, pmd); @@ -143,6 +152,9 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pages += this_pages; } while (pmd++, addr = next, addr != end); + if (mni_start) + mmu_notifier_invalidate_range_end(mm, mni_start, end); + if (nr_huge_updates) count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); return pages; @@ -205,12 +217,12 @@ unsigned long change_protection(struct vm_area_struct *vma, unsigned long start, struct mm_struct *mm = vma->vm_mm; unsigned long pages; - mmu_notifier_invalidate_range_start(mm, start, end); - if (is_vm_hugetlb_page(vma)) + if (is_vm_hugetlb_page(vma)) { + mmu_notifier_invalidate_range_start(mm, start, end); pages = hugetlb_change_protection(vma, start, end, newprot); - else + mmu_notifier_invalidate_range_end(mm, start, end); + } else pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa); - mmu_notifier_invalidate_range_end(mm, start, end); return pages; } -- 1.8.5.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2014-02-18 22:13 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-02-18 22:12 [PATCH -mm 0/3] fix numa vs kvm scalability issue riel 2014-02-18 22:12 ` riel 2014-02-18 22:12 ` [PATCH -mm 1/3] sched,numa: add cond_resched to task_numa_work riel 2014-02-18 22:12 ` riel 2014-02-21 20:32 ` [tip:sched/urgent] " tip-bot for Rik van Riel 2014-02-18 22:12 ` [PATCH -mm 2/3] mm,numa: reorganize change_pmd_range riel 2014-02-18 22:12 ` riel 2014-02-19 2:22 ` David Rientjes 2014-02-19 2:22 ` David Rientjes 2014-02-18 22:12 ` riel [this message] 2014-02-18 22:12 ` [PATCH -mm 3/3] move mmu notifier call from change_protection to change_pmd_range riel 2014-02-19 2:24 ` David Rientjes 2014-02-19 2:24 ` David Rientjes 2014-02-19 3:08 ` Rik van Riel 2014-02-19 3:08 ` Rik van Riel 2014-02-19 3:18 ` [PATCH -mm v2 " Rik van Riel 2014-02-19 3:18 ` Rik van Riel 2014-02-19 8:59 ` [PATCH -mm 0/3] fix numa vs kvm scalability issue Peter Zijlstra 2014-02-19 8:59 ` Peter Zijlstra 2014-02-19 19:28 ` Andrew Morton 2014-02-19 19:28 ` Andrew Morton
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