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| author | Alexey Gladkov <legion@kernel.org> | 2024-01-15 18:46:42 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-02-23 02:38:52 +0300 |
| commit | 9220066ea807e3efce21476bffcac16743e9db22 (patch) | |
| tree | 03b0331dad1db446d68ce32e15fb376411955999 | |
| parent | 50ec499b9a43e46200c9f7b7d723ab2e4af540b3 (diff) | |
| download | linux-9220066ea807e3efce21476bffcac16743e9db22.tar.xz | |
docs: add information about ipc sysctls limitations
After 25b21cb2f6d6 ("[PATCH] IPC namespace core") and 4e9823111bdc
("[PATCH] IPC namespace - shm") the shared memory page count stopped being
global and started counting per ipc namespace. The documentation and
shmget(2) still says that shmall is a global option.
shmget(2):
SHMALL System-wide limit on the total amount of shared memory, measured in
units of the system page size. On Linux, this limit can be read and
modified via /proc/sys/kernel/shmall.
I think the changes made in 2006 should be documented.
Link: https://lkml.kernel.org/r/09e99911071766958af488beb4e8a728a4f12135.1705333426.git.legion@kernel.org
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://lkml.kernel.org/r/ede20ddf7be48b93e8084c3be2e920841ee1a641.1663756794.git.legion@kernel.org
Cc: Christian Brauner <brauner@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Joel Granados <joel.granados@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | Documentation/admin-guide/sysctl/kernel.rst | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index 6584a1f9bfe3..bc578663619d 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -594,6 +594,9 @@ default (``MSGMNB``). ``msgmni`` is the maximum number of IPC queues. 32000 by default (``MSGMNI``). +All of these parameters are set per ipc namespace. The maximum number of bytes +in POSIX message queues is limited by ``RLIMIT_MSGQUEUE``. This limit is +respected hierarchically in the each user namespace. msg_next_id, sem_next_id, and shm_next_id (System V IPC) ======================================================== @@ -1274,15 +1277,20 @@ are doing anyway :) shmall ====== -This parameter sets the total amount of shared memory pages that -can be used system wide. Hence, ``shmall`` should always be at least -``ceil(shmmax/PAGE_SIZE)``. +This parameter sets the total amount of shared memory pages that can be used +inside ipc namespace. The shared memory pages counting occurs for each ipc +namespace separately and is not inherited. Hence, ``shmall`` should always be at +least ``ceil(shmmax/PAGE_SIZE)``. If you are not sure what the default ``PAGE_SIZE`` is on your Linux system, you can run the following command:: # getconf PAGE_SIZE +To reduce or disable the ability to allocate shared memory, you must create a +new ipc namespace, set this parameter to the required value and prohibit the +creation of a new ipc namespace in the current user namespace or cgroups can +be used. shmmax ====== |