[PATCH v10 RESEND 3/3] Documentation: kdump: Add description of enable multi-cpus support

From: Baoquan He
Date: Mon Sep 19 2016 - 02:00:47 EST

From: Zhou Wenjian <zhouwj-fnst@xxxxxxxxxxxxxx>

Multi-cpu support is useful to improve the performance of kdump in
some cases. So add the description of enable multi-cpu support in
dump-capture kernel.

Signed-off-by: Zhou Wenjian <zhouwj-fnst@xxxxxxxxxxxxxx>
Acked-by: Baoquan He <bhe@xxxxxxxxxx>
Acked-by: Xunlei Pang <xpang@xxxxxxxxxx>
Documentation/kdump/kdump.txt | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index f7ef340..b0eb27b 100644
--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -396,6 +396,13 @@ Notes on loading the dump-capture kernel:
Note, though maxcpus always works, you had better replace it with
nr_cpus to save memory if supported by the current ARCH, such as x86.

+* You should enable multi-cpu support in dump-capture kernel if you intend
+ to use multi-thread programs with it, such as parallel dump feature of
+ makedumpfile. Otherwise, the multi-thread program may have a great
+ performance degradation. To enable multi-cpu support, you should bring up an
+ SMP dump-capture kernel and specify maxcpus/nr_cpus, disable_cpu_apicid=[X]
+ options while loading it.
* For s390x there are two kdump modes: If a ELF header is specified with
the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
is done on all other architectures. If no elfcorehdr= kernel parameter is