[mm] [PATCH 2/4] Add the soft limit interface v2

Balbir Singh
2008-02-19T07:07:48Z

A new configuration file called soft_limit_in_bytes is added. The parsing
and configuration rules remain the same as for the limit_in_bytes user
interface.

A global list of all memory cgroups over their soft limit is maintained.
This list is then used to reclaim memory on global pressure. A cgroup is
removed from the list when the cgroup is deleted.

The global list is protected with a read-write spinlock.

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---

mm/memcontrol.c | 33 ++++++++++++++++++++++++++++++++-
1 file changed, 32 insertions(+), 1 deletion(-)

diff -puN mm/memcontrol.c~memory-controller-add-soft-limit-interface mm/memcontrol.c
--- linux-2.6.25-rc2/mm/memcontrol.c~memory-controller-add-soft-limit-interface 2008-02-19 12:31:49.000000000 +0530
+++ linux-2.6.25-rc2-balbir/mm/memcontrol.c 2008-02-19 12:31:49.000000000 +0530
@@ -35,6 +35,10 @@

struct cgroup_subsys mem_cgroup_subsys;
static const int MEM_CGROUP_RECLAIM_RETRIES = 5;
+static spinlock_t mem_cgroup_sl_list_lock; /* spin lock that protects */
+ /* the list of cgroups over*/
+ /* their soft limit */
+static struct list_head mem_cgroup_sl_exceeded_list;

/*
* Statistics for memory cgroup.
@@ -136,6 +140,10 @@ struct mem_cgroup {
* statistics.
*/
struct mem_cgroup_stat stat;
+ /*
+ * List of all mem_cgroup's that exceed their soft limit
+ */
+ struct list_head sl_exceeded_list;
};

/*
@@ -679,6 +687,18 @@ retry:
goto retry;
}

+ /*
+ * If we exceed our soft limit, we get added to the list of
+ * cgroups over their soft limit
+ */
+ if (!res_counter_check_under_limit(&mem->res, RES_SOFT_LIMIT)) {
+ spin_lock_irqsave(&mem_cgroup_sl_list_lock, flags);
+ if (list_empty(&mem->sl_exceeded_list))
+ list_add_tail(&mem->sl_exceeded_list,
+ &mem_cgroup_sl_exceeded_list);
+ spin_unlock_irqrestore(&mem_cgroup_sl_list_lock, flags);
+ }
+
mz = page_cgroup_zoneinfo(pc);
spin_lock_irqsave(&mz->lru_lock, flags);
/* Update statistics vector */
@@ -736,13 +756,14 @@ void mem_cgroup_uncharge(struct page_cgr
if (atomic_dec_and_test(&pc->ref_cnt)) {
page = pc->page;
mz = page_cgroup_zoneinfo(pc);
+ mem = pc->mem_cgroup;
/*
* get page->cgroup and clear it under lock.
* force_empty can drop page->cgroup without checking refcnt.
*/
unlock_page_cgroup(page);
+
if (clear_page_cgroup(page, pc) == pc) {
- mem = pc->mem_cgroup;
css_put(&mem->css);
res_counter_uncharge(&mem->res, PAGE_SIZE);
spin_lock_irqsave(&mz->lru_lock, flags);
@@ -1046,6 +1067,12 @@ static struct cftype mem_cgroup_files[]
.name = "stat",
.open = mem_control_stat_open,
},
+ {
+ .name = "soft_limit_in_bytes",
+ .private = RES_SOFT_LIMIT,
+ .write = mem_cgroup_write,
+ .read = mem_cgroup_read,
+ },
};

static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
@@ -1097,6 +1124,9 @@ mem_cgroup_create(struct cgroup_subsys *
if (unlikely((cont->parent) == NULL)) {
mem = &init_mem_cgroup;
init_mm.mem_cgroup = mem;
+ INIT_LIST_HEAD(&mem->sl_exceeded_list);
+ spin_lock_init(&mem_cgroup_sl_list_lock);
+ INIT_LIST_HEAD(&mem_cgroup_sl_exceeded_list);
} else
mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);

@@ -1104,6 +1134,7 @@ mem_cgroup_create(struct cgroup_subsys *
return NULL;

res_counter_init(&mem->res);
+ INIT_LIST_HEAD(&mem->sl_exceeded_list);

memset(&mem->info, 0, sizeof(mem->info));

_