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[Bug 1564475] Re: 128M is not enough for kdump on s390 LPARs
This bug was fixed in the package zipl-installer - 0.0.33ubuntu3
zipl-installer (0.0.33ubuntu3) xenial; urgency=medium
* Reluctantly Bump crashkernel to 196M, as otherwise 128M is not enough
by default to collect a kdump on any LPAR, defeating the intended
purpose in the first place. (LP: #1564475)
-- Dimitri John Ledkov <xnox@xxxxxxxxxx> Mon, 11 Apr 2016 12:49:46
** Changed in: zipl-installer (Ubuntu Xenial)
Status: In Progress => Fix Released
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128M is not enough for kdump on s390 LPARs
Status in Ubuntu on IBM z Systems:
Status in makedumpfile package in Ubuntu:
Status in s390-tools package in Ubuntu:
Status in zipl-installer package in Ubuntu:
Status in makedumpfile source package in Xenial:
Status in s390-tools source package in Xenial:
Status in zipl-installer source package in Xenial:
== Comment: #0 - Michael Holzheu <michael.holzheu@xxxxxxxxxx> - 2016-03-31 10:59:26 ==
With the current Ubuntu default setting "crashkernel=128M" kdump on LPARs crashes with out-of-memory (see attachment "dmesg_lpar_out_of_mem_128M.txt").
On z/VM guests 128M seems to be sufficient.
One reason on our test LPAR is that a lot of devices are attached (see
attachment "lscss_lpar.txt") which are not required for kdump but
consume a lot of memory because the s390 CIO layer allocates data
structures in the kernel for those devices.
We can disable the devices by using the "cio_ignore=" kernel parameter
in "/etc/default/kdump-tools". For example, on our LPAR that uses DASD
0.0.e934 for /var/crash, we added the following line to disable the
For more information on the "cio_ignore=" kernel parameter see:
Even with "cio_ignore=" we still get out-of-memory with
With "crashkernel=196M" and "cio_ignore=" we are able to create a dump
on our LPAR. We currently do not know why kdump with "cio_ignore=" on
LPAR consumes more memory than on z/VM guests.
== Comment: #1 - Michael Holzheu <michael.holzheu@xxxxxxxxxx> - 2016-03-31 11:03:15 ==
Kernel messages of kdump out-of-memory crash on LPAR with many devices without cio_ignore parameter and 128M crashkernel memory.
== Comment: #2 - Michael Holzheu <michael.holzheu@xxxxxxxxxx> - 2016-03-31 11:04:10 ==
Output of lscss showing all attached (not online) devices on the LPAR.
== Comment: #3 - Michael Holzheu <michael.holzheu@xxxxxxxxxx> - 2016-03-31 11:07:35 ==
To solve this issue our recommendation is:
1) Increase "crashkernel=" default to 196M on Ubuntu for s390.
2) Document that KDUMP_CMDLINE_APPEND with "cio_ignore=" can be used
to decrease memory consumption for kdump on systems with many devices
that are not required for kdump.
The most user friendly solution would be to automatically determine
the required kdump devices and set the correct "cio_ignore=" kernel
parameter. But this is not trivial, because it can be difficult to
find out the required devices for stacked setups like LVM or for
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