Add much needed descriptions for a number of the IPC related sysctl OIDs.

This information will be very useful for people who are tuning applications
which have a dependence on IPC mechanisms.

The following OIDs were documented:

Message queues:
 kern.ipc.msgmax
 kern.ipc.msgmni
 kern.ipc.msgmnb
 kern.ipc.msgtlq
 kern.ipc.msgssz
 kern.ipc.msgseg

Semaphores:
 kern.ipc.semmap
 kern.ipc.semmni
 kern.ipc.semmns
 kern.ipc.semmnu
 kern.ipc.semmsl
 kern.ipc.semopm
 kern.ipc.semume
 kern.ipc.semusz
 kern.ipc.semvmx
 kern.ipc.semaem

Shared memory:
 kern.ipc.shmmax
 kern.ipc.shmmin
 kern.ipc.shmmni
 kern.ipc.shmseg
 kern.ipc.shmall
 kern.ipc.shm_use_phys
 kern.ipc.shm_allow_removed
 kern.ipc.shmsegs

These new descriptions can be viewed using sysctl -d

PR:		kern/65219
Submitted by:	Dan Nelson <dnelson at allantgroup dot com> (modified)
No objections:	developers@
Descriptions reviewed by: gnn
MFC after:	1 week

3 files changed, 47 insertions, 24 deletions

diff --git a/sys/kern/sysv_msg.c b/sys/kern/sysv_msg.c
index f1a7122..60a9431 100644
--- a/sys/kern/sysv_msg.c
+++ b/sys/kern/sysv_msg.c
@@ -1312,11 +1312,17 @@ sysctl_msqids(SYSCTL_HANDLER_ARGS)
 }
 
 SYSCTL_DECL(_kern_ipc);
-SYSCTL_INT(_kern_ipc, OID_AUTO, msgmax, CTLFLAG_RD, &msginfo.msgmax, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, msgmni, CTLFLAG_RDTUN, &msginfo.msgmni, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, msgmnb, CTLFLAG_RDTUN, &msginfo.msgmnb, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, msgtql, CTLFLAG_RDTUN, &msginfo.msgtql, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, msgssz, CTLFLAG_RDTUN, &msginfo.msgssz, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, msgseg, CTLFLAG_RDTUN, &msginfo.msgseg, 0, "");
+SYSCTL_INT(_kern_ipc, OID_AUTO, msgmax, CTLFLAG_RD, &msginfo.msgmax, 0,
+    "Maximum message size");
+SYSCTL_INT(_kern_ipc, OID_AUTO, msgmni, CTLFLAG_RDTUN, &msginfo.msgmni, 0,
+    "Number of message queue identifiers");
+SYSCTL_INT(_kern_ipc, OID_AUTO, msgmnb, CTLFLAG_RDTUN, &msginfo.msgmnb, 0,
+    "Maximum number of bytes in a queue");
+SYSCTL_INT(_kern_ipc, OID_AUTO, msgtql, CTLFLAG_RDTUN, &msginfo.msgtql, 0,
+    "Maximum number of messages in the system");
+SYSCTL_INT(_kern_ipc, OID_AUTO, msgssz, CTLFLAG_RDTUN, &msginfo.msgssz, 0,
+    "Size of a message segment");
+SYSCTL_INT(_kern_ipc, OID_AUTO, msgseg, CTLFLAG_RDTUN, &msginfo.msgseg, 0,
+    "Number of message segments");
 SYSCTL_PROC(_kern_ipc, OID_AUTO, msqids, CTLFLAG_RD,
     NULL, 0, sysctl_msqids, "", "Message queue IDs");
diff --git a/sys/kern/sysv_sem.c b/sys/kern/sysv_sem.c
index 0adcaa3..b406f98 100644
--- a/sys/kern/sysv_sem.c
+++ b/sys/kern/sysv_sem.c
@@ -197,16 +197,26 @@ struct seminfo seminfo = {
 };
 
 SYSCTL_DECL(_kern_ipc);
-SYSCTL_INT(_kern_ipc, OID_AUTO, semmap, CTLFLAG_RW, &seminfo.semmap, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, semmni, CTLFLAG_RDTUN, &seminfo.semmni, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, semmns, CTLFLAG_RDTUN, &seminfo.semmns, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, semmnu, CTLFLAG_RDTUN, &seminfo.semmnu, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, semmsl, CTLFLAG_RW, &seminfo.semmsl, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, semopm, CTLFLAG_RDTUN, &seminfo.semopm, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, semume, CTLFLAG_RDTUN, &seminfo.semume, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, semusz, CTLFLAG_RDTUN, &seminfo.semusz, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, semvmx, CTLFLAG_RW, &seminfo.semvmx, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, semaem, CTLFLAG_RW, &seminfo.semaem, 0, "");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semmap, CTLFLAG_RW, &seminfo.semmap, 0,
+    "Number of entries in the semaphore map");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semmni, CTLFLAG_RDTUN, &seminfo.semmni, 0,
+    "Number of semaphore identifiers");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semmns, CTLFLAG_RDTUN, &seminfo.semmns, 0,
+    "Maximum number of semaphores in the system");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semmnu, CTLFLAG_RDTUN, &seminfo.semmnu, 0,
+    "Maximum number of undo structures in the system");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semmsl, CTLFLAG_RW, &seminfo.semmsl, 0,
+    "Max semaphores per id");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semopm, CTLFLAG_RDTUN, &seminfo.semopm, 0,
+    "Max operations per semop call");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semume, CTLFLAG_RDTUN, &seminfo.semume, 0,
+    "Max undo entries per process");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semusz, CTLFLAG_RDTUN, &seminfo.semusz, 0,
+    "Size in bytes of undo structure");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semvmx, CTLFLAG_RW, &seminfo.semvmx, 0,
+    "Semaphore maximum value");
+SYSCTL_INT(_kern_ipc, OID_AUTO, semaem, CTLFLAG_RW, &seminfo.semaem, 0,
+    "Adjust on exit max value");
 SYSCTL_PROC(_kern_ipc, OID_AUTO, sema, CTLFLAG_RD,
     NULL, 0, sysctl_sema, "", "");
 
diff --git a/sys/kern/sysv_shm.c b/sys/kern/sysv_shm.c
index 7566ebb..b205999 100644
--- a/sys/kern/sysv_shm.c
+++ b/sys/kern/sysv_shm.c
@@ -177,17 +177,24 @@ static int shm_use_phys;
 static int shm_allow_removed;
 
 SYSCTL_DECL(_kern_ipc);
-SYSCTL_INT(_kern_ipc, OID_AUTO, shmmax, CTLFLAG_RW, &shminfo.shmmax, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, shmmin, CTLFLAG_RW, &shminfo.shmmin, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, shmmni, CTLFLAG_RDTUN, &shminfo.shmmni, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, shmseg, CTLFLAG_RDTUN, &shminfo.shmseg, 0, "");
-SYSCTL_INT(_kern_ipc, OID_AUTO, shmall, CTLFLAG_RW, &shminfo.shmall, 0, "");
+SYSCTL_INT(_kern_ipc, OID_AUTO, shmmax, CTLFLAG_RW, &shminfo.shmmax, 0,
+    "Maximum shared memory segment size");
+SYSCTL_INT(_kern_ipc, OID_AUTO, shmmin, CTLFLAG_RW, &shminfo.shmmin, 0,
+    "Minimum shared memory segment size");
+SYSCTL_INT(_kern_ipc, OID_AUTO, shmmni, CTLFLAG_RDTUN, &shminfo.shmmni, 0,
+    "Number of shared memory identifiers");
+SYSCTL_INT(_kern_ipc, OID_AUTO, shmseg, CTLFLAG_RDTUN, &shminfo.shmseg, 0,
+    "Number of segments per process");
+SYSCTL_INT(_kern_ipc, OID_AUTO, shmall, CTLFLAG_RW, &shminfo.shmall, 0,
+    "Maximum number of pages available for shared memory");
 SYSCTL_INT(_kern_ipc, OID_AUTO, shm_use_phys, CTLFLAG_RW,
-    &shm_use_phys, 0, "");
+    &shm_use_phys, 0, "Enable/Disable locking of shared memory pages in core");
 SYSCTL_INT(_kern_ipc, OID_AUTO, shm_allow_removed, CTLFLAG_RW,
-    &shm_allow_removed, 0, "");
+    &shm_allow_removed, 0,
+    "Enable/Disable attachment to attached segments marked for removal");
 SYSCTL_PROC(_kern_ipc, OID_AUTO, shmsegs, CTLFLAG_RD,
-    NULL, 0, sysctl_shmsegs, "", "");
+    NULL, 0, sysctl_shmsegs, "",
+    "Current number of shared memory segments allocated");
 
 static int
 shm_find_segment_by_key(key)