[RFC PATCH 1/4] [RESEND] Scaling msgmni to the amount of lowmem

Nadia.Derbey
2008-01-14T15:58:17Z

[-- Attachment #1: ipc_scale_msgmni_with_lowmem.patch --]
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[PATCH 01/04]

This patch computes msg_ctlmni to make it scale with the amount of lowmem.
msg_ctlmni is now set to make the message queues occupy 1/32 of the available
lowmem.

Some cleaning has also been done in the MSGXXX constants:
. MSGPOOL: the msgctl man page says it's not used, but it also defines it as
a size in bytes (the code expresses it in Kbytes).
. MSGSEG definition has been removed since it used only once in msgctl().

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

---
include/linux/msg.h | 14 +++++++++++---
ipc/msg.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 53 insertions(+), 5 deletions(-)

Index: linux-2.6.24-rc7/include/linux/msg.h
===================================================================
--- linux-2.6.24-rc7.orig/include/linux/msg.h 2008-01-11 14:08:41.000000000 +0100
+++ linux-2.6.24-rc7/include/linux/msg.h 2008-01-11 14:50:47.000000000 +0100
@@ -49,17 +49,25 @@ struct msginfo {
unsigned short msgseg;
};

+/*
+ * Scaling factor to compute msgmni:
+ * the memory dedicated to msg queues (msgmni * msgmnb) should occupy
+ * at most 1/MSG_MEM_SCALE of the lowmem (see the formula in ipc/msg.c):
+ * up to 8MB : msgmni = 16 (MSGMNI)
+ * 4 GB : msgmni = 8K
+ * more than 16 GB : msgmni = 32K (IPCMNI)
+ */
+#define MSG_MEM_SCALE 32
+
#define MSGMNI 16 /* <= IPCMNI */ /* max # of msg queue identifiers */
#define MSGMAX 8192 /* <= INT_MAX */ /* max size of message (bytes) */
#define MSGMNB 16384 /* <= INT_MAX */ /* default max size of a message queue */

/* unused */
-#define MSGPOOL (MSGMNI*MSGMNB/1024) /* size in kilobytes of message pool */
+#define MSGPOOL (MSGMNI * MSGMNB) /* size in bytes of message pool */
#define MSGTQL MSGMNB /* number of system message headers */
#define MSGMAP MSGMNB /* number of entries in message map */
#define MSGSSZ 16 /* message segment size */
-#define __MSGSEG ((MSGPOOL*1024)/ MSGSSZ) /* max no. of segments */
-#define MSGSEG (__MSGSEG <= 0xffff ? __MSGSEG : 0xffff)

#ifdef __KERNEL__
#include <linux/list.h>
Index: linux-2.6.24-rc7/ipc/msg.c
===================================================================
--- linux-2.6.24-rc7.orig/ipc/msg.c 2008-01-11 14:08:48.000000000 +0100
+++ linux-2.6.24-rc7/ipc/msg.c 2008-01-11 15:51:00.000000000 +0100
@@ -27,6 +27,7 @@
#include <linux/msg.h>
#include <linux/spinlock.h>
#include <linux/init.h>
+#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/list.h>
#include <linux/security.h>
@@ -79,12 +80,51 @@ static int newque(struct ipc_namespace *
static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
#endif

+/*
+ * Scale msgmni with the available lowmem size: the memory dedicated to msg
+ * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
+ */
+static void recompute_msgmni(struct ipc_namespace *ns)
+{
+ struct sysinfo i;
+ unsigned long allowed;
+
+ si_meminfo(&i);
+ allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
+ / MSGMNB;
+
+ /*
+ * Never fall under the current minimum value
+ */
+ if (allowed < MSGMNI) {
+ ns->msg_ctlmni = MSGMNI;
+ goto out_callback;
+ }
+
+ /*
+ * Never go over the current max value
+ */
+ if (allowed > IPCMNI) {
+ ns->msg_ctlmni = IPCMNI;
+ goto out_callback;
+ }
+
+ ns->msg_ctlmni = allowed;
+
+out_callback:
+
+ printk(KERN_INFO "msgmni has been set to %d for ipc namespace %p\n",
+ ns->msg_ctlmni, ns);
+}
+
static void __msg_init_ns(struct ipc_namespace *ns, struct ipc_ids *ids)
{
ns->ids[IPC_MSG_IDS] = ids;
ns->msg_ctlmax = MSGMAX;
ns->msg_ctlmnb = MSGMNB;
- ns->msg_ctlmni = MSGMNI;
+
+ recompute_msgmni(ns);
+
atomic_set(&ns->msg_bytes, 0);
atomic_set(&ns->msg_hdrs, 0);
ipc_init_ids(ids);
@@ -458,7 +498,7 @@ asmlinkage long sys_msgctl(int msqid, in
msginfo.msgmax = ns->msg_ctlmax;
msginfo.msgmnb = ns->msg_ctlmnb;
msginfo.msgssz = MSGSSZ;
- msginfo.msgseg = MSGSEG;
+ msginfo.msgseg = min(MSGPOOL / MSGSSZ, 0xffff);
down_read(&msg_ids(ns).rw_mutex);
if (cmd == MSG_INFO) {
msginfo.msgpool = msg_ids(ns).in_use;

--