** Changed in: makedumpfile (Ubuntu Xenial)
Status: New => In Progress
** Changed in: makedumpfile (Ubuntu Xenial)
Importance: Undecided => Low
** Description changed:
+ [SRU justification]
+ Use a more restrictive kernel boot option to limit CPU numbers to 1
+
+ [Impact]
+ Will significantly lower crashkernel memory usage on some architectures
(namely ppc64el)
+
+ [Fix]
+ Change the maxcpus boot parameter used in the kexec command by nr_cpus.
+
+ [Test Case]
+ kexec-config show will display maxcpus=1 without the change. It will show
nr_cpus=1 with the proposed change.
+
+ [Regression]
+ None expected, nr_cpus is a more generic parameter and is more restrictive
than the previous parameter.
+
+ [Original Problem Description of the problem]
== Comment: #0 - Ping Tian Han - 2016-04-07 23:04:30 ==
---Problem Description---
Because canonical has fixed bug 137281 ( LP: #1560552 ) in 4.4.0-17-generic,
the kernel now supports "nr_cpus=1". So we should update the "maxcpus=1" to
"nr_cpus=1" in /etc/default/kdump-tools I think.
-
+
---uname output---
Linux thymelp2 4.4.0-17-generic #33-Ubuntu SMP Tue Mar 29 17:15:31 UTC 2016
ppc64le ppc64le ppc64le GNU/Linux
-
- Userspace tool: kdump-tools version 1:1.5.9-5
+
+ Userspace tool: kdump-tools version 1:1.5.9-5
== Comment: #2 - Hari Krishna Bathini - 2016-04-11 04:36:14 ==
(In reply to comment #1)
> Hari.
- >
+ >
> Would you please validate that nr_cpus is consistent across architectures
> and should become the new default?
- >
+ >
> Thanks.
Hi Kevin,
I know nr_cpus=1 is supported on x86 based on this patch
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=14cb6dcf0a023f5977461c94d8d5a163c937979b
About other architectures, I am not really sure.
But looking at the kdump-tools source package, it seems like other
architectures
are using maxcpus=1 to boot kdump kernel unless there is architecture specific
overrides that are missing in the source. Canonical might be able to answer
better.
If other aren't using or willing to use nr_cpus=1, we may need a patch
of this kind:
diff --git a/kdump-config b/kdump-config
index 0ff0e6f..aba300e 100755
--- a/kdump-config
+++ b/kdump-config
@@ -48,7 +48,11 @@ KDUMP_COREDIR=${KDUMP_COREDIR:=/var/crash}
- KDUMP_DUMP_DMESG=${KDUMP_DUMP_DMESG:=1}
- KDUMP_DIR="/var/lib/kdump"
- MAKEDUMP_ARGS=${MAKEDUMP_ARGS:="-c -d 31"}
+ KDUMP_DUMP_DMESG=${KDUMP_DUMP_DMESG:=1}
+ KDUMP_DIR="/var/lib/kdump"
+ MAKEDUMP_ARGS=${MAKEDUMP_ARGS:="-c -d 31"}
-KDUMP_CMDLINE_APPEND=${KDUMP_CMDLINE_APPEND:="irqpoll maxcpus=1 nousb
systemd.unit=kdump-tools.service"}
+if [ "$ARCH" = "ppc64le" ]; then
+ KDUMP_CMDLINE_APPEND=${KDUMP_CMDLINE_APPEND:="irqpoll nr_cpus=1 nousb
systemd.unit=kdump-tools.service"}
+else
+ KDUMP_CMDLINE_APPEND=${KDUMP_CMDLINE_APPEND:="irqpoll maxcpus=1 nousb
systemd.unit=kdump-tools.service"}
+fi
- KDUMP_KERNEL_HOOK="/etc/kernel/postinst.d/kdump-tools"
- [ -d $KDUMP_COREDIR ] || mkdir -p $KDUMP_COREDIR ;
+ KDUMP_KERNEL_HOOK="/etc/kernel/postinst.d/kdump-tools"
+ [ -d $KDUMP_COREDIR ] || mkdir -p $KDUMP_COREDIR ;
== Comment: #4 - Kevin W. Rudd - 2016-04-11 11:08:16 ==
Mirroring to Canonical for their review and feedback.
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https://bugs.launchpad.net/bugs/1568952
Title:
ISST-LTE:pVM:thymelp2:ubuntu 16.04: change "maxcpus=1" to "nr_cpus=1"
in kdump-tools
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