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Subject[PATCH v3 6/7] tcp buffer limitation: per-cgroup limit
Date
This patch uses the "tcp_max_mem" field of the kmem_cgroup to
effectively control the amount of kernel memory pinned by a cgroup.

We have to make sure that none of the memory pressure thresholds
specified in the namespace are bigger than the current cgroup.

Signed-off-by: Glauber Costa <glommer@parallels.com>
CC: David S. Miller <davem@davemloft.net>
CC: Hiroyouki Kamezawa <kamezawa.hiroyu@jp.fujitsu.com>
CC: Eric W. Biederman <ebiederm@xmission.com>
---
Documentation/cgroups/memory.txt | 1 +
include/linux/memcontrol.h | 10 ++++
mm/memcontrol.c | 89 +++++++++++++++++++++++++++++++++++---
net/ipv4/sysctl_net_ipv4.c | 20 ++++++++
4 files changed, 113 insertions(+), 7 deletions(-)
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 6f1954a..1ffde3e 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -78,6 +78,7 @@ Brief summary of control files.

memory.independent_kmem_limit # select whether or not kernel memory limits are
independent of user limits
+ memory.kmem.tcp.max_memory # set/show hard limit for tcp buf memory

1. History

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6b8c0c0..2df6db8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -416,6 +416,9 @@ int tcp_init_cgroup_fill(struct proto *prot, struct cgroup *cgrp,
struct cgroup_subsys *ss);
void tcp_destroy_cgroup(struct proto *prot, struct cgroup *cgrp,
struct cgroup_subsys *ss);
+
+unsigned long tcp_max_memory(struct mem_cgroup *cg);
+void tcp_prot_mem(struct mem_cgroup *cg, long val, int idx);
#else
/* memcontrol includes sockets.h, that includes memcontrol.h ... */
static inline void memcg_sock_mem_alloc(struct mem_cgroup *mem,
@@ -441,6 +444,13 @@ static inline void sock_update_memcg(struct sock *sk)
static inline void sock_release_memcg(struct sock *sk)
{
}
+static inline unsigned long tcp_max_memory(struct mem_cgroup *cg)
+{
+ return 0;
+}
+static inline void tcp_prot_mem(struct mem_cgroup *cg, long val, int idx)
+{
+}
#endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
#endif /* CONFIG_INET */
#endif /* _LINUX_MEMCONTROL_H */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5e9b2c7..be5ab89 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -345,6 +345,7 @@ struct mem_cgroup {
spinlock_t pcp_counter_lock;

/* per-cgroup tcp memory pressure knobs */
+ int tcp_max_memory;
atomic_long_t tcp_memory_allocated;
struct percpu_counter tcp_sockets_allocated;
/* those two are read-mostly, leave them at the end */
@@ -352,6 +353,11 @@ struct mem_cgroup {
int tcp_memory_pressure;
};

+static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
+{
+ return (mem == root_mem_cgroup);
+}
+
static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
/* Writing them here to avoid exposing memcg's inner layout */
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
@@ -466,6 +472,56 @@ struct percpu_counter *sockets_allocated_tcp(struct mem_cgroup *sg)
return &sg->tcp_sockets_allocated;
}

+static int tcp_write_maxmem(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+ struct mem_cgroup *sg = mem_cgroup_from_cont(cgrp);
+ struct mem_cgroup *parent = parent_mem_cgroup(sg);
+ struct net *net = current->nsproxy->net_ns;
+ int i;
+
+ if (!cgroup_lock_live_group(cgrp))
+ return -ENODEV;
+
+ /*
+ * We can't allow more memory than our parents. Since this
+ * will be tested for all calls, by induction, there is no need
+ * to test any parent other than our own
+ * */
+ if (parent && (val > parent->tcp_max_memory))
+ val = parent->tcp_max_memory;
+
+ sg->tcp_max_memory = val;
+
+ for (i = 0; i < 3; i++)
+ sg->tcp_prot_mem[i] = min_t(long, val,
+ net->ipv4.sysctl_tcp_mem[i]);
+
+ cgroup_unlock();
+
+ return 0;
+}
+
+static u64 tcp_read_maxmem(struct cgroup *cgrp, struct cftype *cft)
+{
+ struct mem_cgroup *sg = mem_cgroup_from_cont(cgrp);
+ u64 ret;
+
+ if (!cgroup_lock_live_group(cgrp))
+ return -ENODEV;
+ ret = sg->tcp_max_memory;
+
+ cgroup_unlock();
+ return ret;
+}
+
+static struct cftype tcp_files[] = {
+ {
+ .name = "kmem.tcp.max_memory",
+ .write_u64 = tcp_write_maxmem,
+ .read_u64 = tcp_read_maxmem,
+ },
+};
+
/*
* For ipv6, we only need to fill in the function pointers (can't initialize
* things twice). So keep it separated
@@ -487,8 +543,10 @@ int tcp_init_cgroup(struct proto *prot, struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
struct mem_cgroup *cg = mem_cgroup_from_cont(cgrp);
+ struct mem_cgroup *parent = parent_mem_cgroup(cg);
unsigned long limit;
struct net *net = current->nsproxy->net_ns;
+ int ret = 0;

cg->tcp_memory_pressure = 0;
atomic_long_set(&cg->tcp_memory_allocated, 0);
@@ -497,12 +555,25 @@ int tcp_init_cgroup(struct proto *prot, struct cgroup *cgrp,
limit = nr_free_buffer_pages() / 8;
limit = max(limit, 128UL);

+ if (parent)
+ cg->tcp_max_memory = parent->tcp_max_memory;
+ else
+ cg->tcp_max_memory = limit * 2;
+
cg->tcp_prot_mem[0] = net->ipv4.sysctl_tcp_mem[0];
cg->tcp_prot_mem[1] = net->ipv4.sysctl_tcp_mem[1];
cg->tcp_prot_mem[2] = net->ipv4.sysctl_tcp_mem[2];

tcp_init_cgroup_fill(prot, cgrp, ss);
- return 0;
+ /*
+ * For non-root cgroup, we need to set up all tcp-related variables,
+ * but to be consistent with the rest of kmem management, we don't
+ * expose any of the controls
+ */
+ if (!mem_cgroup_is_root(cg))
+ ret = cgroup_add_files(cgrp, ss, tcp_files,
+ ARRAY_SIZE(tcp_files));
+ return ret;
}
EXPORT_SYMBOL(tcp_init_cgroup);

@@ -514,6 +585,16 @@ void tcp_destroy_cgroup(struct proto *prot, struct cgroup *cgrp,
percpu_counter_destroy(&cg->tcp_sockets_allocated);
}
EXPORT_SYMBOL(tcp_destroy_cgroup);
+
+unsigned long tcp_max_memory(struct mem_cgroup *cg)
+{
+ return cg->tcp_max_memory;
+}
+
+void tcp_prot_mem(struct mem_cgroup *cg, long val, int idx)
+{
+ cg->tcp_prot_mem[idx] = val;
+}
#endif /* CONFIG_INET */
#endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */

@@ -1092,12 +1173,6 @@ static struct mem_cgroup *mem_cgroup_get_next(struct mem_cgroup *iter,
#define for_each_mem_cgroup_all(iter) \
for_each_mem_cgroup_tree_cond(iter, NULL, true)

-
-static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
-{
- return (mem == root_mem_cgroup);
-}
-
void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
{
struct mem_cgroup *mem;
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index bbd67ab..cdc35f6 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -14,6 +14,7 @@
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/nsproxy.h>
+#include <linux/memcontrol.h>
#include <linux/swap.h>
#include <net/snmp.h>
#include <net/icmp.h>
@@ -182,6 +183,10 @@ static int ipv4_tcp_mem(ctl_table *ctl, int write,
int ret;
unsigned long vec[3];
struct net *net = current->nsproxy->net_ns;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+ int i;
+ struct mem_cgroup *cg;
+#endif

ctl_table tmp = {
.data = &vec,
@@ -198,6 +203,21 @@ static int ipv4_tcp_mem(ctl_table *ctl, int write,
if (ret)
return ret;

+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+ rcu_read_lock();
+ cg = mem_cgroup_from_task(current);
+ for (i = 0; i < 3; i++)
+ if (vec[i] > tcp_max_memory(cg)) {
+ rcu_read_unlock();
+ return -EINVAL;
+ }
+
+ tcp_prot_mem(cg, vec[0], 0);
+ tcp_prot_mem(cg, vec[1], 1);
+ tcp_prot_mem(cg, vec[2], 2);
+ rcu_read_unlock();
+#endif
+
net->ipv4.sysctl_tcp_mem[0] = vec[0];
net->ipv4.sysctl_tcp_mem[1] = vec[1];
net->ipv4.sysctl_tcp_mem[2] = vec[2];
--
1.7.6


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