Messages in this thread Patch in this message | | | Date | Fri, 06 Jun 2008 08:10:01 +0200 | From | <> | Subject | [RFC -mm 6/6] sysv ipc: documentation for msgmnb scaling wrt. cpus |
| |
From: Solofo Ramangalahy <Solofo.Ramangalahy@bull.net>
Add documentation to explain how to disable and reenable the computation mechanism.
Signed-off-by: Solofo Ramangalahy <Solofo.Ramangalahy@bull.net>
---
Documentation/sysctl/kernel.txt | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+)
Index: b/Documentation/sysctl/kernel.txt =================================================================== --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -179,6 +179,33 @@ kernel stack. ============================================================== +msgmnb + +Maximum size in bytes, not in message count, of a single SystemV IPC +message queue (b stands for bytes). + +This value is dynamic and depends on the online cpu count of the +machine (taking cpu hotplug into account). + +Computed values are between MSGMNB and MSGMNB*MSG_CPU_SCALE #define +constants (currently [16384,65536]). + +The exact value is automatically (re)computed, but: +. If the value is positioned from user space (via procfs or sysctl()), + to a positive value then the automatic recomputation is + disabled. This leaves control to user space. E.g. + + # echo 16384 > /proc/sys/kernel/msgmnb + +. If the value is positioned from user space to a negative value, then + the computation is reenabled. E.g. + + # echo -1 > /proc/sys/kernel/msgmnb + +See recompute_msgmnb() function in ipc/ directory for details. + +============================================================== + osrelease, ostype & version: # cat osrelease -- Solofo Ramangalahy Bull SA.
| |