On 10/04/2011 04:57 AM, KAMEZAWA Hiroyuki wrote:

On Mon,  3 Oct 2011 14:18:38 +0400
Glauber Costa[off-list ref]  wrote:

quoted

This patch converts struct sock fields memory_pressure,
memory_allocated, sockets_allocated, and sysctl_mem (now prot_mem)
to function pointers, receiving a struct mem_cgroup parameter.

enter_memory_pressure is kept the same, since all its callers
have socket a context, and the kmem_cgroup can be derived from
the socket itself.

To keep things working, the patch convert all users of those fields
to use acessor functions.

In my benchmarks I didn't see a significant performance difference
with this patch applied compared to a baseline (around 1 % diff, thus
inside error margin).

Signed-off-by: Glauber Costa<redacted>
CC: David S. Miller<davem@davemloft.net>
CC: Hiroyouki Kamezawa<redacted>
CC: Eric W. Biederman<redacted>

A nitpick.

quoted

  #ifdef CONFIG_INET
  struct sock;
+struct proto;
  #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
  void sock_update_memcg(struct sock *sk);
  void sock_release_memcg(struct sock *sk);
-
+void memcg_sock_mem_alloc(struct mem_cgroup *mem, struct proto *prot,
+			  int amt, int *parent_failure);
+void memcg_sock_mem_free(struct mem_cgroup *mem, struct proto *prot, int amt);
+void memcg_sockets_allocated_dec(struct mem_cgroup *mem, struct proto *prot);
+void memcg_sockets_allocated_inc(struct mem_cgroup *mem, struct proto *prot);
  #else
+/* memcontrol includes sockets.h, that includes memcontrol.h ... */
+static inline void memcg_sock_mem_alloc(struct mem_cgroup *mem,
+					struct proto *prot, int amt,
+					int *parent_failure)
+{
+}

In these days, at naming memory cgroup pointers, we use "memcg" instead of
"mem". So, could you use "memcg" for represeinting memory cgroup ?

quoted

+
+void memcg_sock_mem_alloc(struct mem_cgroup *mem, struct proto *prot,
+			  int amt, int *parent_failure)
+{
+	mem = parent_mem_cgroup(mem);
+	for (; mem != NULL; mem = parent_mem_cgroup(mem)) {
+		long alloc;
+		long *prot_mem = prot->prot_mem(mem);
+		/*
+		 * Large nestings are not the common case, and stopping in the
+		 * middle would be complicated enough, that we bill it all the
+		 * way through the root, and if needed, unbill everything later
+		 */
+		alloc = atomic_long_add_return(amt,
+					       prot->memory_allocated(mem));
+		*parent_failure |= (alloc>  prot_mem[2]);
+	}
+}
+EXPORT_SYMBOL(memcg_sock_mem_alloc);

Hmm. why not using res_counter ? for reusing 'unbill' code ?

Well,

res_counters are slightly more expensive than needed here, since we need 
to clear interrupts and hold a spinlock. No particular reason besides it.


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