Commit 296c81d8 authored by Balbir Singh's avatar Balbir Singh Committed by Linus Torvalds
Browse files

memory controller: soft limit interface



Add an interface to allow get/set of soft limits.  Soft limits for memory
plus swap controller (memsw) is currently not supported.  Resource
counters have been enhanced to support soft limits and new type
RES_SOFT_LIMIT has been added.  Unlike hard limits, soft limits can be
directly set and do not need any reclaim or checks before setting them to
a newer value.

Kamezawa-San raised a question as to whether soft limit should belong to
res_counter.  Since all resources understand the basic concepts of hard
and soft limits, it is justified to add soft limits here.  Soft limits are
a generic resource usage feature, even file system quotas support soft
limits.
Signed-off-by: default avatarBalbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a6df6361
......@@ -34,6 +34,10 @@ struct res_counter {
* the limit that usage cannot exceed
*/
unsigned long long limit;
/*
* the limit that usage can be exceed
*/
unsigned long long soft_limit;
/*
* the number of unsuccessful attempts to consume the resource
*/
......@@ -87,6 +91,7 @@ enum {
RES_MAX_USAGE,
RES_LIMIT,
RES_FAILCNT,
RES_SOFT_LIMIT,
};
/*
......@@ -132,6 +137,36 @@ static inline bool res_counter_limit_check_locked(struct res_counter *cnt)
return false;
}
static inline bool res_counter_soft_limit_check_locked(struct res_counter *cnt)
{
if (cnt->usage < cnt->soft_limit)
return true;
return false;
}
/**
* Get the difference between the usage and the soft limit
* @cnt: The counter
*
* Returns 0 if usage is less than or equal to soft limit
* The difference between usage and soft limit, otherwise.
*/
static inline unsigned long long
res_counter_soft_limit_excess(struct res_counter *cnt)
{
unsigned long long excess;
unsigned long flags;
spin_lock_irqsave(&cnt->lock, flags);
if (cnt->usage <= cnt->soft_limit)
excess = 0;
else
excess = cnt->usage - cnt->soft_limit;
spin_unlock_irqrestore(&cnt->lock, flags);
return excess;
}
/*
* Helper function to detect if the cgroup is within it's limit or
* not. It's currently called from cgroup_rss_prepare()
......@@ -147,6 +182,17 @@ static inline bool res_counter_check_under_limit(struct res_counter *cnt)
return ret;
}
static inline bool res_counter_check_under_soft_limit(struct res_counter *cnt)
{
bool ret;
unsigned long flags;
spin_lock_irqsave(&cnt->lock, flags);
ret = res_counter_soft_limit_check_locked(cnt);
spin_unlock_irqrestore(&cnt->lock, flags);
return ret;
}
static inline void res_counter_reset_max(struct res_counter *cnt)
{
unsigned long flags;
......@@ -180,4 +226,16 @@ static inline int res_counter_set_limit(struct res_counter *cnt,
return ret;
}
static inline int
res_counter_set_soft_limit(struct res_counter *cnt,
unsigned long long soft_limit)
{
unsigned long flags;
spin_lock_irqsave(&cnt->lock, flags);
cnt->soft_limit = soft_limit;
spin_unlock_irqrestore(&cnt->lock, flags);
return 0;
}
#endif
......@@ -19,6 +19,7 @@ void res_counter_init(struct res_counter *counter, struct res_counter *parent)
{
spin_lock_init(&counter->lock);
counter->limit = RESOURCE_MAX;
counter->soft_limit = RESOURCE_MAX;
counter->parent = parent;
}
......@@ -101,6 +102,8 @@ res_counter_member(struct res_counter *counter, int member)
return &counter->limit;
case RES_FAILCNT:
return &counter->failcnt;
case RES_SOFT_LIMIT:
return &counter->soft_limit;
};
BUG();
......
......@@ -2123,6 +2123,20 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
else
ret = mem_cgroup_resize_memsw_limit(memcg, val);
break;
case RES_SOFT_LIMIT:
ret = res_counter_memparse_write_strategy(buffer, &val);
if (ret)
break;
/*
* For memsw, soft limits are hard to implement in terms
* of semantics, for now, we support soft limits for
* control without swap
*/
if (type == _MEM)
ret = res_counter_set_soft_limit(&memcg->res, val);
else
ret = -EINVAL;
break;
default:
ret = -EINVAL; /* should be BUG() ? */
break;
......@@ -2375,6 +2389,12 @@ static struct cftype mem_cgroup_files[] = {
.write_string = mem_cgroup_write,
.read_u64 = mem_cgroup_read,
},
{
.name = "soft_limit_in_bytes",
.private = MEMFILE_PRIVATE(_MEM, RES_SOFT_LIMIT),
.write_string = mem_cgroup_write,
.read_u64 = mem_cgroup_read,
},
{
.name = "failcnt",
.private = MEMFILE_PRIVATE(_MEM, RES_FAILCNT),
......
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