mm: free swap cache aggressively if memcg swap is full

Swap cache pages are freed aggressively if swap is nearly full (>50%
currently), because otherwise we are likely to stop scanning anonymous
when we near the swap limit even if there is plenty of freeable swap cache
pages.  We should follow the same trend in case of memory cgroup, which
has its own swap limit.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bcb38718e174..6a0007965e31 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5761,6 +5761,28 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
 	return nr_swap_pages;
 }
 
+bool mem_cgroup_swap_full(struct page *page)
+{
+	struct mem_cgroup *memcg;
+
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
+
+	if (vm_swap_full())
+		return true;
+	if (!do_swap_account || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
+		return false;
+
+	memcg = page->mem_cgroup;
+	if (!memcg)
+		return false;
+
+	for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg))
+		if (page_counter_read(&memcg->swap) * 2 >= memcg->swap.limit)
+			return true;
+
+	return false;
+}
+
 /* for remember boot option*/
 #ifdef CONFIG_MEMCG_SWAP_ENABLED
 static int really_do_swap_account __initdata = 1;