Hello,
I am not against the modification but would like to understand better the
rationale behind this. According to the kernel doc we have :
maxcpus= [SMP] Maximum number of processors that an SMP kernel
should make use of. maxcpus=n : n >= 0 limits the
kernel to using 'n' processors. n=0 is a special case,
it is equivalent to "nosmp", which also disables
the IO APIC.
nr_cpus= [SMP] Maximum number of processors that an SMP kernel
could support. nr_cpus=n : n >= 1 limits the kernel to
supporting 'n' processors. Later in runtime you can not
use hotplug cpu feature to put more cpu back to online.
just like you compile the kernel NR_CPUS=n
I personally would be inclined to use maxcpus=0 and totally disable SMP
but I am opened to other options.
Kind regards,
...Louis
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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
Status in makedumpfile package in Ubuntu:
New
Bug description:
== 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
== 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=${MAKEDUMP_ARGS:="-c -d 31"}
-KDUMP_CMDLINE_APPEND=${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 ;
== Comment: #4 - Kevin W. Rudd - 2016-04-11 11:08:16 ==
Mirroring to Canonical for their review and feedback.
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