quoted

+ * retries
+ */
+#define NR_PAGES_TO_RETRY 2
+

Should be 1 << PAGE_ALLOC_COSTLY_ORDER?  Where does this number come from?
The changelog doesn't specify.

Hocko complained about that, and I changed. Where the number comes from, 
is stated in the comments: it is a number small enough to have high 
changes of had been freed by the previous reclaim, and yet around the 
number of pages of a kernel allocation.

Of course there are allocations for nr_pages > 2. But 2 will already 
service the stack most of the time, and most of the slab caches.

quoted

  static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
-				unsigned int nr_pages, bool oom_check)
+				unsigned int nr_pages, unsigned int min_pages,
+				bool oom_check)
  {
  	unsigned long csize = nr_pages * PAGE_SIZE;
  	struct mem_cgroup *mem_over_limit;

@@ -2182,18 +2190,18 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
  	} else
  		mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
  	/*
-	 * nr_pages can be either a huge page (HPAGE_PMD_NR), a batch
-	 * of regular pages (CHARGE_BATCH), or a single regular page (1).
-	 *
  	 * Never reclaim on behalf of optional batching, retry with a
  	 * single page instead.
  	 */
-	if (nr_pages == CHARGE_BATCH)
+	if (nr_pages > min_pages)
  		return CHARGE_RETRY;

  	if (!(gfp_mask & __GFP_WAIT))
  		return CHARGE_WOULDBLOCK;

+	if (gfp_mask & __GFP_NORETRY)
+		return CHARGE_NOMEM;
+
  	ret = mem_cgroup_reclaim(mem_over_limit, gfp_mask, flags);
  	if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
  		return CHARGE_RETRY;

@@ -2206,7 +2214,7 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
  	 * unlikely to succeed so close to the limit, and we fall back
  	 * to regular pages anyway in case of failure.
  	 */
-	if (nr_pages == 1 && ret)
+	if (nr_pages <= NR_PAGES_TO_RETRY && ret)
  		return CHARGE_RETRY;

  	/*

@@ -2341,7 +2349,8 @@ again:
  			nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
  		}

-		ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, oom_check);
+		ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, nr_pages,
+		    oom_check);
  		switch (ret) {
  		case CHARGE_OK:
  			break;