From: Rik van Riel <r...@redhat.com>
commit a5338093bfb462256f70f3450c08f73e59543e26 upstream
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 <r...@redhat.com>
Acked-by: David Rientjes <rient...@google.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Andrea Arcangeli <aarca...@redhat.com>
Reported-by: Xing Gang <gang.x...@hp.com>
Tested-by: Chegu Vinod <chegu_vi...@hp.com>
Cc: Sasha Levin <sasha.le...@oracle.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Yang Shi <yang....@windriver.com>
---
mm/hugetlb.c | 2 ++
mm/mprotect.c | 15 ++++++++++++---
2 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4901fc9..d02c665 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3356,6 +3356,7 @@ unsigned long hugetlb_change_protection(struct
vm_area_struct *vma,
BUG_ON(address >= end);
flush_cache_range(vma, address, end);
+ mmu_notifier_invalidate_range_start(mm, start, end);
mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
for (; address < end; address += huge_page_size(h)) {
spinlock_t *ptl;
@@ -3385,6 +3386,7 @@ unsigned long hugetlb_change_protection(struct
vm_area_struct *vma,
*/
flush_tlb_range(vma, start, end);
mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
+ mmu_notifier_invalidate_range_end(mm, start, end);
return pages << h->order;
}
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 79cb518..2afc40e 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;
@@ -202,15 +214,12 @@ unsigned long change_protection(struct vm_area_struct
*vma, unsigned long start,
unsigned long end, pgprot_t newprot,
int dirty_accountable, int prot_numa)
{
- struct mm_struct *mm = vma->vm_mm;
unsigned long pages;
- mmu_notifier_invalidate_range_start(mm, start, end);
if (is_vm_hugetlb_page(vma))
pages = hugetlb_change_protection(vma, start, end, newprot);
else
pages = change_protection_range(vma, start, end, newprot,
dirty_accountable, prot_numa);
- mmu_notifier_invalidate_range_end(mm, start, end);
return pages;
}
--
2.0.2
--
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