@thorsten If I understand correctly cio_ignore command needs to be on the running instance that is about to crash, rather than on the re-exec kernel. Thus it needs to be computed and added to e.g. /etc/zipl.conf. At the moment we do not generate/update /etc/zipl.conf in an automated way, but the more I think about it the better it sounds to e.g. able to specify all crashdump parameters, computed cio_ignore, correct root= argument, and generate menu items for every installed ubuntu kernel (rather than just the last one), and recovery stanzas too. I'll open a wishlist bug about that.
BTW, does it make sense to compute and use `cio_ignore -k -u` generated command line by default? on one hand kernel will use less memory, on the other hand `lszdev` will be quite empty and one will have a harder time to discover additional devices one can bring online. I have, for now, added things to https://wiki.ubuntu.com/S390X -> feel free to edit and/or improve that. And I will open a new bug report to get those updates into the Ubuntu Server Guide. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to makedumpfile in Ubuntu. https://bugs.launchpad.net/bugs/1564475 Title: 128M is not enough for kdump on s390 LPARs Status in Ubuntu on IBM z Systems: Fix Released Status in makedumpfile package in Ubuntu: Invalid Status in s390-tools package in Ubuntu: Fix Released Status in zipl-installer package in Ubuntu: Fix Released Status in makedumpfile source package in Xenial: Invalid Status in s390-tools source package in Xenial: Fix Released Status in zipl-installer source package in Xenial: Fix Released Bug description: == Comment: #0 - Michael Holzheu <michael.holz...@de.ibm.com> - 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 devices: KDUMP_CMDLINE_APPEND="irqpoll maxcpus=1 cio_ignore=all,!condev,!0.0.e934" For more information on the "cio_ignore=" kernel parameter see: https://github.com/torvalds/linux/blob/master/Documentation/s390/CommonIO Even with "cio_ignore=" we still get out-of-memory with "crashkernel=128M". 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.holz...@de.ibm.com> - 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.holz...@de.ibm.com> - 2016-03-31 11:04:10 == Output of lscss showing all attached (not online) devices on the LPAR. == Comment: #3 - Michael Holzheu <michael.holz...@de.ibm.com> - 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 network dump. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1564475/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
