[RFC][PATCH v2 2/7] Scaling msgmni to the number of ipc namespaces

[Nadia.Derbey at bull.net]

[PATCH 02/07]

Since all the namespaces see the same amount of memory (the total one)
this patch introduces a new variable that counts the ipc namespaces and
divides msg_ctlmni by this counter.

Signed-off-by: Nadia Derbey <Nadia.Derbey at bull.net>

---
 include/linux/ipc.h |    1 +
 ipc/msg.c           |   10 +++++++---
 ipc/util.c          |    7 +++++++
 3 files changed, 15 insertions(+), 3 deletions(-)

Index: linux-2.6.24/include/linux/ipc.h
===================================================================
--- linux-2.6.24.orig/include/linux/ipc.h	2008-01-29 16:54:38.000000000 +0100
+++ linux-2.6.24/include/linux/ipc.h	2008-01-31 10:03:47.000000000 +0100
@@ -121,6 +121,7 @@ struct ipc_namespace {
 };
 
 extern struct ipc_namespace init_ipc_ns;
+extern atomic_t nr_ipc_ns;
 
 #ifdef CONFIG_SYSVIPC
 #define INIT_IPC_NS(ns)		.ns		= &init_ipc_ns,
Index: linux-2.6.24/ipc/util.c
===================================================================
--- linux-2.6.24.orig/ipc/util.c	2008-01-29 16:55:04.000000000 +0100
+++ linux-2.6.24/ipc/util.c	2008-01-31 10:05:58.000000000 +0100
@@ -51,6 +51,9 @@ struct ipc_namespace init_ipc_ns = {
 	},
 };
 
+atomic_t nr_ipc_ns = ATOMIC_INIT(1);
+
+
 static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
 {
 	int err;
@@ -61,6 +64,8 @@ static struct ipc_namespace *clone_ipc_n
 	if (ns == NULL)
 		goto err_mem;
 
+	atomic_inc(&nr_ipc_ns);
+
 	err = sem_init_ns(ns);
 	if (err)
 		goto err_sem;
@@ -80,6 +85,7 @@ err_msg:
 	sem_exit_ns(ns);
 err_sem:
 	kfree(ns);
+	atomic_dec(&nr_ipc_ns);
 err_mem:
 	return ERR_PTR(err);
 }
@@ -109,6 +115,7 @@ void free_ipc_ns(struct kref *kref)
 	msg_exit_ns(ns);
 	shm_exit_ns(ns);
 	kfree(ns);
+	atomic_dec(&nr_ipc_ns);
 }
 
 /**
Index: linux-2.6.24/ipc/msg.c
===================================================================
--- linux-2.6.24.orig/ipc/msg.c	2008-01-31 09:58:25.000000000 +0100
+++ linux-2.6.24/ipc/msg.c	2008-01-31 10:08:49.000000000 +0100
@@ -83,24 +83,28 @@ static int sysvipc_msg_proc_show(struct 
 /*
  * Scale msgmni with the available lowmem size: the memory dedicated to msg
  * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
- * This should be done staying within the (MSGMNI , IPCMNI) range.
+ * Also take into account the number of nsproxies created so far.
+ * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
  */
 static void recompute_msgmni(struct ipc_namespace *ns)
 {
 	struct sysinfo i;
 	unsigned long allowed;
+	int nb_ns;
 
 	si_meminfo(&i);
 	allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
 		/ MSGMNB;
+	nb_ns = atomic_read(&nr_ipc_ns);
+	allowed /= nb_ns;
 
 	if (allowed < MSGMNI) {
 		ns->msg_ctlmni = MSGMNI;
 		goto out_callback;
 	}
 
-	if (allowed > IPCMNI) {
-		ns->msg_ctlmni = IPCMNI;
+	if (allowed > IPCMNI / nb_ns) {
+		ns->msg_ctlmni = IPCMNI / nb_ns;
 		goto out_callback;
 	}
 

--