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authorWaiman Long <longman@redhat.com>2019-05-15 01:46:29 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-15 05:52:52 +0300
commit5ac893b8cb10fe2a47a77780d37f9bf5b142854b (patch)
tree9d6dcab9f8540b997090f6870a0470cf6bfd06cc /Documentation
parenta5091fda4e3c202aeb1728a86d0fcd20fd0f4f5e (diff)
downloadlinux-5ac893b8cb10fe2a47a77780d37f9bf5b142854b.tar.xz
ipc: allow boot time extension of IPCMNI from 32k to 16M
The maximum number of unique System V IPC identifiers was limited to 32k. That limit should be big enough for most use cases. However, there are some users out there requesting for more, especially those that are migrating from Solaris which uses 24 bits for unique identifiers. To satisfy the need of those users, a new boot time kernel option "ipcmni_extend" is added to extend the IPCMNI value to 16M. This is a 512X increase which should be big enough for users out there that need a large number of unique IPC identifier. The use of this new option will change the pattern of the IPC identifiers returned by functions like shmget(2). An application that depends on such pattern may not work properly. So it should only be used if the users really need more than 32k of unique IPC numbers. This new option does have the side effect of reducing the maximum number of unique sequence numbers from 64k down to 128. So it is a trade-off. The computation of a new IPC id is not done in the performance critical path. So a little bit of additional overhead shouldn't have any real performance impact. Link: http://lkml.kernel.org/r/20190329204930.21620-1-longman@redhat.com Signed-off-by: Waiman Long <longman@redhat.com> Acked-by: Manfred Spraul <manfred@colorfullife.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kees Cook <keescook@chromium.org> Cc: "Luis R. Rodriguez" <mcgrof@kernel.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Takashi Iwai <tiwai@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt3
1 files changed, 3 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 80e40de446c0..d1d1da911085 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1830,6 +1830,9 @@
ip= [IP_PNP]
See Documentation/filesystems/nfs/nfsroot.txt.
+ ipcmni_extend [KNL] Extend the maximum number of unique System V
+ IPC identifiers from 32,768 to 16,777,216.
+
irqaffinity= [SMP] Set the default irq affinity mask
The argument is a cpu list, as described above.