linux-kernel - [PATCH v2] Documentation: kdump: add description of bringing up SMP dump-capture kernel

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Message-ID: <1470010988-18050-1-git-send-email-zhouwj-fnst@cn.fujitsu.com>
Date:	Mon, 1 Aug 2016 08:23:08 +0800
From:	Zhou Wenjian <zhouwj-fnst@...fujitsu.com>
To:	<linux-kernel@...r.kernel.org>
CC:	<kexec@...ts.infradead.org>, <bhe@...hat.com>, <dyoung@...hat.com>,
	<d.hatayama@...fujitsu.com>
Subject: [PATCH v2] Documentation: kdump: add description of bringing up SMP dump-capture kernel

v1->v2: change nr_cpus to maxcpus

SMP dump-capture kernel is useful to improve the performance of kdump in
some cases. So add the description of bringing up SMP dump-capture kernel.

Signed-off-by: Zhou Wenjian <zhouwj-fnst@...fujitsu.com>
---
 Documentation/kdump/kdump.txt | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index 88ff63d..c5762b7 100644
--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -394,6 +394,12 @@ Notes on loading the dump-capture kernel:
   dump. Hence generally it is useful either to build a UP dump-capture
   kernel or specify maxcpus=1 option while loading dump-capture kernel.
 
+* We should bring up a SMP dump-capture kernel if we intend to use multi-threads
+  programs with it, such as parallel dump feature of makedumpfile. Otherwise,
+  the multi-threads program may have a great performance degradation.
+  To bring up a SMP dump-capture kernel, we should specify maxcpus=[X] and
+  disable_cpu_apic=[Y] 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