linux-kernel - [PATCH v9 2/2] Documentation: kdump: add description of enable multi-cpus support

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Date:	Thu, 18 Aug 2016 11:11:47 +0800
From:	Zhou Wenjian <zhouwj-fnst@...fujitsu.com>
To:	<linux-kernel@...r.kernel.org>
CC:	<akpm@...ux-foundation.org>, <dyoung@...hat.com>, <bhe@...hat.com>,
	<vgoyal@...hat.com>, <corbet@....net>, <kexec@...ts.infradead.org>,
	<linux-doc@...r.kernel.org>, <xlpang@...hat.com>, <joe@...ches.com>
Subject: [PATCH v9 2/2] Documentation: kdump: add description of enable multi-cpus support

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@...fujitsu.com>
Acked-by: Baoquan He <bhe@...hat.com>
Acked-by: Xunlei Pang <xpang@...hat.com>
---
 Documentation/kdump/kdump.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index d900080..31e6b88 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 should replace it by 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
-- 
1.8.3.1