diff options
Diffstat (limited to 'include/uapi/linux/msg.h')
| -rw-r--r-- | include/uapi/linux/msg.h | 28 |
1 files changed, 20 insertions, 8 deletions
diff --git a/include/uapi/linux/msg.h b/include/uapi/linux/msg.h index a70375526578..f51c8001dbe5 100644 --- a/include/uapi/linux/msg.h +++ b/include/uapi/linux/msg.h @@ -51,16 +51,28 @@ struct msginfo { }; /* - * 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) + * MSGMNI, MSGMAX and MSGMNB are default values which can be + * modified by sysctl. + * + * MSGMNI is the upper limit for the number of messages queues per + * namespace. + * It has been chosen to be as large possible without facilitating + * scenarios where userspace causes overflows when adjusting the limits via + * operations of the form retrieve current limit; add X; update limit". + * + * MSGMNB is the default size of a new message queue. Non-root tasks can + * decrease the size with msgctl(IPC_SET), root tasks + * (actually: CAP_SYS_RESOURCE) can both increase and decrease the queue + * size. The optimal value is application dependent. + * 16384 is used because it was always used (since 0.99.10) + * + * MAXMAX is the maximum size of an individual message, it's a global + * (per-namespace) limit that applies for all message queues. + * It's set to 1/2 of MSGMNB, to ensure that at least two messages fit into + * the queue. This is also an arbitrary choice (since 2.6.0). */ -#define MSG_MEM_SCALE 32 -#define MSGMNI 16 /* <= IPCMNI */ /* max # of msg queue identifiers */ +#define MSGMNI 32000 /* <= 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 */ |