diff options
| author | Nadia Derbey <Nadia.Derbey@bull.net> | 2008-07-25 01:48:08 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-07-25 10:53:42 -0700 |
| commit | 9eefe520c814f6f62c5d36a2ddcd3fb99dfdb30e (patch) | |
| tree | 064ce99674f144b681f8d365d1e20d99c8078d0c /include | |
| parent | f1a43f93f0f3bab418800eaccb9e2e3b5427e173 (diff) | |
ipc: do not use a negative value to re-enable msgmni automatic recomputing
This patch proposes an alternative to the "magical
positive-versus-negative number trick" Andrew complained about last week
in http://lkml.org/lkml/2008/6/24/418.
This had been introduced with the patches that scale msgmni to the amount
of lowmem. With these patches, msgmni has a registered notification
routine that recomputes msgmni value upon memory add/remove or ipc
namespace creation/ removal.
When msgmni is changed from user space (i.e. value written to the proc
file), that notification routine is unregistered, and the way to make it
registered back is to write a negative value into the proc file. This is
the "magical positive-versus-negative number trick".
To fix this, a new proc file is introduced: /proc/sys/kernel/auto_msgmni.
This file acts as ON/OFF for msgmni automatic recomputing.
With this patch, the process is the following:
1) kernel boots in "automatic recomputing mode"
/proc/sys/kernel/msgmni contains the value that has been computed (depends
on lowmem)
/proc/sys/kernel/automatic_msgmni contains "1"
2) echo <val> > /proc/sys/kernel/msgmni
. sets msg_ctlmni to <val>
. de-activates automatic recomputing (i.e. if, say, some memory is added
msgmni won't be recomputed anymore)
. /proc/sys/kernel/automatic_msgmni now contains "0"
3) echo "0" > /proc/sys/kernel/automatic_msgmni
. de-activates msgmni automatic recomputing
this has the same effect as 2) except that msg_ctlmni's value stays
blocked at its current value)
3) echo "1" > /proc/sys/kernel/automatic_msgmni
. recomputes msgmni's value based on the current available memory size
and number of ipc namespaces
. re-activates automatic recomputing for msgmni.
Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Solofo Ramangalahy <Solofo.Ramangalahy@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/ipc_namespace.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h index ea6c18a8b0d4..ea330f9e7100 100644 --- a/include/linux/ipc_namespace.h +++ b/include/linux/ipc_namespace.h @@ -36,6 +36,7 @@ struct ipc_namespace { int msg_ctlmni; atomic_t msg_bytes; atomic_t msg_hdrs; + int auto_msgmni; size_t shm_ctlmax; size_t shm_ctlall; @@ -53,7 +54,7 @@ extern atomic_t nr_ipc_ns; extern int register_ipcns_notifier(struct ipc_namespace *); extern int cond_register_ipcns_notifier(struct ipc_namespace *); -extern int unregister_ipcns_notifier(struct ipc_namespace *); +extern void unregister_ipcns_notifier(struct ipc_namespace *); extern int ipcns_notify(unsigned long); #else /* CONFIG_SYSVIPC */ |