Commit d51d885b authored Aug 06, 2014 by Johannes Weiner Committed by Linus Torvalds Aug 06, 2014

mm: huge_memory: use GFP_TRANSHUGE when charging huge pages



Transparent huge page charges prefer falling back to regular pages
rather than spending a lot of time in direct reclaim.

Desired reclaim behavior is usually declared in the gfp mask, but THP
charges use GFP_KERNEL and then rely on the fact that OOM is disabled
for THP charges, and that OOM-disabled charges don't retry reclaim.
Needless to say, this is anything but obvious and quite error prone.

Convert THP charges to use GFP_TRANSHUGE instead, which implies
__GFP_NORETRY, to indicate the low-latency requirement.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 28c34c29

mm/huge_memory.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -827,7 +827,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct mm, struct vm_area_struct vma,
		count_vm_event(THP_FAULT_FALLBACK);
		return VM_FAULT_FALLBACK;
		}
		if (unlikely(mem_cgroup_charge_anon(page, mm, GFP_KERNEL))) {
		if (unlikely(mem_cgroup_charge_anon(page, mm, GFP_TRANSHUGE))) {
		put_page(page);
		count_vm_event(THP_FAULT_FALLBACK);
		return VM_FAULT_FALLBACK;
		@@ -1132,7 +1132,7 @@ int do_huge_pmd_wp_page(struct mm_struct mm, struct vm_area_struct vma,
		goto out;
		}

		if (unlikely(mem_cgroup_charge_anon(new_page, mm, GFP_KERNEL))) {
		if (unlikely(mem_cgroup_charge_anon(new_page, mm, GFP_TRANSHUGE))) {
		put_page(new_page);
		if (page) {
		split_huge_page(page);
		@@ -2399,7 +2399,7 @@ static void collapse_huge_page(struct mm_struct *mm,
		if (!new_page)
		return;

		if (unlikely(mem_cgroup_charge_anon(new_page, mm, GFP_KERNEL)))
		if (unlikely(mem_cgroup_charge_anon(new_page, mm, GFP_TRANSHUGE)))
		return;

		/*