[PATCH 4/4] swapcgroup: modify vm_swap_full for cgroup

[Daisuke Nishimura <nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org>]

This patch modifies vm_swap_full() to calculate
the rate of swap usage per cgroup.

The purpose of this change is to free freeable swap caches
(that is, swap entries) per cgroup, so that swap_cgroup_charge()
fails less frequently.

I think I can free freeable swap caches more agressively
with one of Rik's splitlru patchset:

  [patch 04/14] free swap space on swap-in/activation

but, I should verify whether this change to vm_swap_full()
is valid.


Signed-off-by: Daisuke Nishimura <nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org>

---
 include/linux/memcontrol.h |    3 +++
 include/linux/swap.h       |    6 +++++-
 mm/memcontrol.c            |   10 ++++++++++
 mm/memory.c                |    2 +-
 mm/swapfile.c              |   35 ++++++++++++++++++++++++++++++++++-
 5 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a7e6621..256b298 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -179,6 +179,9 @@ extern int swap_cgroup_charge(struct page *page,
 			unsigned long offset);
 extern void swap_cgroup_uncharge(struct swap_info_struct *si,
 				unsigned long offset);
+extern int swap_cgroup_vm_swap_full(struct page *page);
+extern u64 swap_cgroup_read_usage(struct mem_cgroup *mem);
+extern u64 swap_cgroup_read_limit(struct mem_cgroup *mem);
 #else /* CONFIG_CGROUP_SWAP_RES_CTLR */
 static inline int swap_cgroup_charge(struct page *page,
 			struct swap_info_struct *si,
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 18887f0..ef156c9 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -159,8 +159,12 @@ struct swap_list_t {
 	int next;	/* swapfile to be used next */
 };
 
+#ifndef CONFIG_CGROUP_SWAP_RES_CTLR
 /* Swap 50% full? Release swapcache more aggressively.. */
-#define vm_swap_full() (nr_swap_pages*2 < total_swap_pages)
+#define vm_swap_full(page) (nr_swap_pages*2 < total_swap_pages)
+#else
+#define vm_swap_full(page) swap_cgroup_vm_swap_full(page)
+#endif
 
 /* linux/mm/page_alloc.c */
 extern unsigned long totalram_pages;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 84e803d..58d72ca 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1265,5 +1265,15 @@ void swap_cgroup_uncharge(struct swap_info_struct *si,
 		css_put(&mem->css);
 	}
 }
+
+u64 swap_cgroup_read_usage(struct mem_cgroup *mem)
+{
+	return res_counter_read_u64(&mem->swap_res, RES_USAGE);
+}
+
+u64 swap_cgroup_read_limit(struct mem_cgroup *mem)
+{
+	return res_counter_read_u64(&mem->swap_res, RES_LIMIT);
+}
 #endif
 
diff --git a/mm/memory.c b/mm/memory.c
index df8f0e9..be2ff96 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2175,7 +2175,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	page_add_anon_rmap(page, vma, address);
 
 	swap_free(entry);
-	if (vm_swap_full())
+	if (vm_swap_full(page))
 		remove_exclusive_swap_page(page);
 	unlock_page(page);
 
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 682b71e..9256c2d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -429,7 +429,7 @@ void free_swap_and_cache(swp_entry_t entry)
 		/* Only cache user (+us), or swap space full? Free it! */
 		/* Also recheck PageSwapCache after page is locked (above) */
 		if (PageSwapCache(page) && !PageWriteback(page) &&
-					(one_user || vm_swap_full())) {
+					(one_user || vm_swap_full(page))) {
 			delete_from_swap_cache(page);
 			SetPageDirty(page);
 		}
@@ -1892,3 +1892,36 @@ int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
 	*offset = ++toff;
 	return nr_pages? ++nr_pages: 0;
 }
+
+#ifdef CONFIG_CGROUP_SWAP_RES_CTLR
+int swap_cgroup_vm_swap_full(struct page *page)
+{
+	int ret;
+	struct swap_info_struct *p;
+	struct mem_cgroup *mem;
+	u64 usage;
+	u64 limit;
+	swp_entry_t entry;
+
+	VM_BUG_ON(!PageLocked(page));
+	VM_BUG_ON(!PageSwapCache(page));
+
+	ret = 0;
+	entry.val = page_private(page);
+	p = swap_info_get(entry);
+	if (!p)
+		goto out;
+
+	mem = p->memcg[swp_offset(entry)];
+	usage = swap_cgroup_read_usage(mem) / PAGE_SIZE;
+	limit = swap_cgroup_read_limit(mem) / PAGE_SIZE;
+	limit = (limit < total_swap_pages) ? limit : total_swap_pages;
+
+	ret = usage * 2 > limit;
+
+	spin_unlock(&swap_lock);
+
+out:
+	return ret;
+}
+#endif