mm: thp: optimize memcg charge in khugepaged
We don't need to hold the mmmap_sem through mem_cgroup_newpage_charge(),
the mmap_sem is only hold for keeping the vma stable and we don't need the
vma stable anymore after we return from alloc_hugepage_vma().
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 90eef40..615d974 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1771,12 +1771,9 @@
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
#ifndef CONFIG_NUMA
+ up_read(&mm->mmap_sem);
VM_BUG_ON(!*hpage);
new_page = *hpage;
- if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
- up_read(&mm->mmap_sem);
- return;
- }
#else
VM_BUG_ON(*hpage);
/*
@@ -1791,22 +1788,26 @@
*/
new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
node, __GFP_OTHER_NODE);
+
+ /*
+ * After allocating the hugepage, release the mmap_sem read lock in
+ * preparation for taking it in write mode.
+ */
+ up_read(&mm->mmap_sem);
if (unlikely(!new_page)) {
- up_read(&mm->mmap_sem);
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
*hpage = ERR_PTR(-ENOMEM);
return;
}
- count_vm_event(THP_COLLAPSE_ALLOC);
- if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
- up_read(&mm->mmap_sem);
- put_page(new_page);
- return;
- }
#endif
- /* after allocating the hugepage upgrade to mmap_sem write mode */
- up_read(&mm->mmap_sem);
+ count_vm_event(THP_COLLAPSE_ALLOC);
+ if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
+#ifdef CONFIG_NUMA
+ put_page(new_page);
+#endif
+ return;
+ }
/*
* Prevent all access to pagetables with the exception of