memcg: mem+swap controller core
This patch implements per cgroup limit for usage of memory+swap. However
there are SwapCache, double counting of swap-cache and swap-entry is
avoided.
Mem+Swap controller works as following.
- memory usage is limited by memory.limit_in_bytes.
- memory + swap usage is limited by memory.memsw_limit_in_bytes.
This has following benefits.
- A user can limit total resource usage of mem+swap.
Without this, because memory resource controller doesn't take care of
usage of swap, a process can exhaust all the swap (by memory leak.)
We can avoid this case.
And Swap is shared resource but it cannot be reclaimed (goes back to memory)
until it's used. This characteristic can be trouble when the memory
is divided into some parts by cpuset or memcg.
Assume group A and group B.
After some application executes, the system can be..
Group A -- very large free memory space but occupy 99% of swap.
Group B -- under memory shortage but cannot use swap...it's nearly full.
Ability to set appropriate swap limit for each group is required.
Maybe someone wonder "why not swap but mem+swap ?"
- The global LRU(kswapd) can swap out arbitrary pages. Swap-out means
to move account from memory to swap...there is no change in usage of
mem+swap.
In other words, when we want to limit the usage of swap without affecting
global LRU, mem+swap limit is better than just limiting swap.
Accounting target information is stored in swap_cgroup which is
per swap entry record.
Charge is done as following.
map
- charge page and memsw.
unmap
- uncharge page/memsw if not SwapCache.
swap-out (__delete_from_swap_cache)
- uncharge page
- record mem_cgroup information to swap_cgroup.
swap-in (do_swap_page)
- charged as page and memsw.
record in swap_cgroup is cleared.
memsw accounting is decremented.
swap-free (swap_free())
- if swap entry is freed, memsw is uncharged by PAGE_SIZE.
There are people work under never-swap environments and consider swap as
something bad. For such people, this mem+swap controller extension is just an
overhead. This overhead is avoided by config or boot option.
(see Kconfig. detail is not in this patch.)
TODO:
- maybe more optimization can be don in swap-in path. (but not very safe.)
But we just do simple accounting at this stage.
[nishimura@mxp.nes.nec.co.jp: make resize limit hold mutex]
[hugh@veritas.com: memswap controller core swapcache fixes]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 41b46cc..ca51ac7 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -32,6 +32,8 @@
/* for swap handling */
extern int mem_cgroup_try_charge(struct mm_struct *mm,
gfp_t gfp_mask, struct mem_cgroup **ptr);
+extern int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
+ struct page *page, gfp_t mask, struct mem_cgroup **ptr);
extern void mem_cgroup_commit_charge_swapin(struct page *page,
struct mem_cgroup *ptr);
extern void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *ptr);
@@ -80,7 +82,6 @@
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
extern int do_swap_account;
#endif
-
#else /* CONFIG_CGROUP_MEM_RES_CTLR */
struct mem_cgroup;
@@ -97,7 +98,13 @@
}
static inline int mem_cgroup_try_charge(struct mm_struct *mm,
- gfp_t gfp_mask, struct mem_cgroup **ptr)
+ gfp_t gfp_mask, struct mem_cgroup **ptr)
+{
+ return 0;
+}
+
+static inline int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
+ struct page *page, gfp_t gfp_mask, struct mem_cgroup **ptr)
{
return 0;
}
diff --git a/include/linux/swap.h b/include/linux/swap.h
index f8f3907..be938ce 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -214,7 +214,7 @@
extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
gfp_t gfp_mask);
extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
- gfp_t gfp_mask);
+ gfp_t gfp_mask, bool noswap);
extern int __isolate_lru_page(struct page *page, int mode, int file);
extern unsigned long shrink_all_memory(unsigned long nr_pages);
extern int vm_swappiness;
@@ -336,7 +336,7 @@
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
extern int mem_cgroup_cache_charge_swapin(struct page *page,
struct mm_struct *mm, gfp_t mask, bool locked);
-extern void mem_cgroup_uncharge_swapcache(struct page *page);
+extern void mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent);
#else
static inline
int mem_cgroup_cache_charge_swapin(struct page *page,
@@ -344,7 +344,15 @@
{
return 0;
}
-static inline void mem_cgroup_uncharge_swapcache(struct page *page)
+static inline void
+mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
+{
+}
+#endif
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
+extern void mem_cgroup_uncharge_swap(swp_entry_t ent);
+#else
+static inline void mem_cgroup_uncharge_swap(swp_entry_t ent)
{
}
#endif