Add descriptions of parallel dumping and how to use it.
Signed-off-by: Zhou Wenjian zhouwj-fnst@cn.fujitsu.com
v1->v2: 1.fix some inappropriate description 2.delete some unnecessary description --- kexec-kdump-howto.txt | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+)
diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt index 05b497f..3a315d1 100644 --- a/kexec-kdump-howto.txt +++ b/kexec-kdump-howto.txt @@ -616,6 +616,37 @@ options are copied from /proc/cmdline. In general it is best to append command line options using "KDUMP_COMMANDLINE_APPEND=" instead of replacing the original command line completely.
+Parallel Dumping Operation +========================== +Kexec allows kdump using multiple cpus. So parallel feature can accelerate +dumping substantially, especially in executing compress and filter. +For example: + + 1."makedumpfile -c --num-threads [THREAD_NUM] /proc/vmcore dumpfile" + 2."makedumpfile -c /proc/vmcore dumpfile", + + 1 has better performance than 2, if THREAD_NUM is larger than two + and the usable cpus number is larger than THREAD_NUM. + +Notes on how to use multiple cpus on a capture kernel on x86 system: + +Make sure that you are using a kernel that supports disable_cpu_apicid +kernel option as a capture kernel, which is needed to avoid x86 specific +hardware issue (*). The disable_cpu_apicid kernel option is automatically +appended by kdumpctl script and is ignored if the kernel doesn't support it. + +You need to specify how many cpus to be used in a capture kernel by specifying +the number of cpus in nr_cpus kernel option in /etc/sysconfig/kdump. nr_cpus +is 1 at default. + +You should use necessary and suffcient number of cpus on a capture kernel. +IOW, don't use too many cpus on a capture kernel, or the capture kernel may +lead to panic due to Out Of Memory(each cpu uses about 1MB). + +(*) Without disable_cpu_apicid kernel option, capture kernel leads to hang, +system reset or power-off at boot, depending on your system and runtime +situation at the time of crash. + Debugging Tips -------------- - One can drop into a shell before/after saving vmcore with the help of
On 16/09/2015:02:56:20 PM, Zhou Wenjian wrote:
Add descriptions of parallel dumping and how to use it.
Signed-off-by: Zhou Wenjian zhouwj-fnst@cn.fujitsu.com
v1->v2: 1.fix some inappropriate description 2.delete some unnecessary description
No, No..
Sorry, if I could not explain it clearly. changelog should come after ---, otherwise it will become part of the patch.
So when you have done `git format-patch ......`, you have a 0001-xxxx.patch Now you hand edit that 0001-xxxx.patch and add commit log just after ---.
~Pratyush
On 09/16/2015 03:33 PM, Pratyush Anand wrote:
On 16/09/2015:02:56:20 PM, Zhou Wenjian wrote:
Add descriptions of parallel dumping and how to use it.
Signed-off-by: Zhou Wenjian zhouwj-fnst@cn.fujitsu.com
v1->v2: 1.fix some inappropriate description 2.delete some unnecessary description
No, No..
Sorry, if I could not explain it clearly. changelog should come after ---, otherwise it will become part of the patch.
So when you have done `git format-patch ......`, you have a 0001-xxxx.patch Now you hand edit that 0001-xxxx.patch and add commit log just after ---.
~Pratyush
Thanks for telling me. I'll fix that in v3.