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Diffstat (limited to 'Documentation/admin-guide/sysctl/kernel.rst')
| -rw-r--r-- | Documentation/admin-guide/sysctl/kernel.rst | 43 |
1 files changed, 35 insertions, 8 deletions
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index 6584a1f9bfe3..7fd43947832f 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 ====== |