2008-06-06 06:17:55

by Solofo.Ramangalahy

[permalink] [raw]
Subject: [RFC -mm 1/6] sysv ipc: scale msgmnb to the number of cpus

From: Solofo Ramangalahy <[email protected]>

Initialize msgmnb value to
min(MSGMNB * num_online_cpus(), MSGMNB * MSG_CPU_SCALE)
to increase the default value for larger machines.

MSG_CPU_SCALE scaling factor is defined to be 4, as 16384 x 4 = 65536
is an already used and recommended value.

The msgmni value is made dependant of msgmnb to keep the memory
dedicated to message queues within the 1/MSG_MEM_SCALE of lowmem
bound.

Unlike msgmni, the value is not scaled (down) with respect to the
number of ipc namespaces for simplicity.

Signed-off-by: Solofo Ramangalahy <[email protected]>

---
include/linux/msg.h | 5 +++++
ipc/msg.c | 19 +++++++++++++++----
2 files changed, 20 insertions(+), 4 deletions(-)

Index: b/ipc/msg.c
===================================================================
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -38,6 +38,7 @@
#include <linux/rwsem.h>
#include <linux/nsproxy.h>
#include <linux/ipc_namespace.h>
+#include <linux/cpumask.h>

#include <asm/current.h>
#include <asm/uaccess.h>
@@ -92,7 +93,7 @@ void recompute_msgmni(struct ipc_namespa

si_meminfo(&i);
allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
- / MSGMNB;
+ / ns->msg_ctlmnb;
nb_ns = atomic_read(&nr_ipc_ns);
allowed /= nb_ns;

@@ -108,11 +109,21 @@ void recompute_msgmni(struct ipc_namespa

ns->msg_ctlmni = allowed;
}
+/*
+ * Scale msgmnb with the number of online cpus, up to 4x MSGMNB.
+ * ns->msg_ctlmnb cannot be assigned zero because of division in
+ * recompute_msgmni()
+ */
+void recompute_msgmnb(struct ipc_namespace *ns)
+{
+ ns->msg_ctlmnb =
+ min(MSGMNB * num_online_cpus(), MSGMNB * MSG_CPU_SCALE);
+}

void msg_init_ns(struct ipc_namespace *ns)
{
ns->msg_ctlmax = MSGMAX;
- ns->msg_ctlmnb = MSGMNB;
+ recompute_msgmnb(ns);

recompute_msgmni(ns);

@@ -132,8 +143,8 @@ void __init msg_init(void)
{
msg_init_ns(&init_ipc_ns);

- printk(KERN_INFO "msgmni has been set to %d\n",
- init_ipc_ns.msg_ctlmni);
+ printk(KERN_INFO "msgmni has been set to %d, msgmnb to %d\n",
+ init_ipc_ns.msg_ctlmni, init_ipc_ns.msg_ctlmnb);

ipc_init_proc_interface("sysvipc/msg",
" key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n",
Index: b/include/linux/msg.h
===================================================================
--- a/include/linux/msg.h
+++ b/include/linux/msg.h
@@ -58,6 +58,11 @@ struct msginfo {
* more than 16 GB : msgmni = 32K (IPCMNI)
*/
#define MSG_MEM_SCALE 32
+/*
+ * Scaling factor to compute msgmnb:
+ * ns->msg_ctlmnb is between MSGMNB and MSGMNB * MSG_CPU_SCALE
+ */
+#define MSG_CPU_SCALE 4

#define MSGMNI 16 /* <= IPCMNI */ /* max # of msg queue identifiers */
#define MSGMAX 8192 /* <= INT_MAX */ /* max size of message (bytes) */

--
Solofo Ramangalahy
Bull SA.