5ac893b8cb
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> |
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| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.