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-rw-r--r--Documentation/admin-guide/sysctl/kernel.rst43
1 files changed, 35 insertions, 8 deletions
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 6584a1f9bf..7fd4394783 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -296,12 +296,30 @@ kernel panic). This will output the contents of the ftrace buffers to
the console. This is very useful for capturing traces that lead to
crashes and outputting them to a serial console.
-= ===================================================
-0 Disabled (default).
-1 Dump buffers of all CPUs.
-2 Dump the buffer of the CPU that triggered the oops.
-= ===================================================
+======================= ===========================================
+0 Disabled (default).
+1 Dump buffers of all CPUs.
+2(orig_cpu) Dump the buffer of the CPU that triggered the
+ oops.
+<instance> Dump the specific instance buffer on all CPUs.
+<instance>=2(orig_cpu) Dump the specific instance buffer on the CPU
+ that triggered the oops.
+======================= ===========================================
+Multiple instance dump is also supported, and instances are separated
+by commas. If global buffer also needs to be dumped, please specify
+the dump mode (1/2/orig_cpu) first for global buffer.
+
+So for example to dump "foo" and "bar" instance buffer on all CPUs,
+user can::
+
+ echo "foo,bar" > /proc/sys/kernel/ftrace_dump_on_oops
+
+To dump global buffer and "foo" instance buffer on all
+CPUs along with the "bar" instance buffer on CPU that triggered the
+oops, user can::
+
+ echo "1,foo,bar=2" > /proc/sys/kernel/ftrace_dump_on_oops
ftrace_enabled, stack_tracer_enabled
====================================
@@ -594,6 +612,9 @@ 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)
========================================================
@@ -850,6 +871,7 @@ bit 3 print locks info if ``CONFIG_LOCKDEP`` is on
bit 4 print ftrace buffer
bit 5 print all printk messages in buffer
bit 6 print all CPUs backtrace (if available in the arch)
+bit 7 print only tasks in uninterruptible (blocked) state
===== ============================================
So for example to print tasks and memory info on panic, user can::
@@ -1274,15 +1296,20 @@ 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
======