On Fri, Nov 8, 2019 at 5:18 PM van Sleeuwen, Berry <[email protected]> wrote: > > Hi Stefan, > > Thanks for this information. So an update looks like the first step. > > After initial installation I updated with the most current ports-mirror. The > current version is VERSION="18.04.3 LTS (Bionic Beaver)". Looking at it, > indeed the kernel was updated to 4.15.0-66 after I got the repo available but > there is also an 4.18.0-25 available in there. However this 4.18 version was > not installed.
Thanks Stefan, yeah [1] really looks good in regard to the issue described here. This fix is indeed in newer kernels like the 4.18 HWE kernel, but btw the most recent HWE kernel for 18.04 is even already at 5.0.0.34.91. Anyway, this won't help the defaults, as you can see on [2] that for compatibility reasons "Server installations will default to the GA kernel and provide the enablement kernel as optional." So without users like Berry explicitly opting into the new kernel they won't get the fix. Given that this issue potentially affects the install when enabling plenty of disks I wonder if the change should be backported to an update of the GA kernel into a 4.15-0-xx release. @Stefan you are the Author and the patch looks rather small and backportable. Also for potential regressions of that default change [1] states that there were none of the expected performance regressions happening. What would be your opinion, should we open a bug and ask the Kernel team to consider backporting this into Ubuntu's 4.15 kernel as well? [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3284da34a87ab7a527a593f89bbdaf6debe9e713 [2]: https://wiki.ubuntu.com/Kernel/LTSEnablementStack#Ubuntu_18.04_LTS_-_Bionic_Beaver > > Met vriendelijke groet/With kind regards/Mit freundlichen Grüßen, > Berry van Sleeuwen > Flight Forum 3000 5657 EW Eindhoven > > -----Original Message----- > From: Linux on 390 Port <[email protected]> On Behalf Of Stefan > Haberland > Sent: Friday, November 08, 2019 4:11 PM > To: [email protected] > Subject: Re: Ubuntu 18-04 unable to add DASD > > On 07.11.19 15:55, van Sleeuwen, Berry wrote: > > Hi All, > > > > I have installed an Ubuntu 19-04 but as it turns out the application > > requires version 18-04. So I have installed a new 18-04 system. > > > > Next I tried to move the LVM from the 19-04 machine into the 18-04 machine. > > But I can't get the disks online. The first few disks are fine but at a > > certain point the server crashes. During "chccwdev -e" at some point all > > memory is exhausted and I see a lot of CPU and IO. Eventually the > > OOM-killer kicks in to kill various processes. The server is no longer > > responding and only a reboot (force and xautolog) will get the server back > > online. > > > > Next I have added a new range of disks instead of reusing the old. > > Unfortunately with the empty disks I got into the same situation. But > > eventually, after formatting the disks one-by-one, I was able to get a new > > filesystem available. Even during reboot the new filesystem is activated > > without a problem. So it looks like for some reason the problem went away. > > But when I add another filesystem the machine once again crashes during > > activation of the disks. > > > > What could cause this to happen? I am reluctant to hand over this machine > > as we might get into the same problem when we need to add additional disks. > > Hi Berry, > > what exact kernel version are we talking about? Unfortunately after start > using blk-mq the DASD driver used a lot of memory for a single device due to > a quite optimistic number of hardware queues and queue depth. This was > significantly improved with > > commit 3284da34a87a ("s390/dasd: reduce the default queue depth and nr of > hardware queues") > > which is available since kernel 4.18. This is should be available in Ubuntu > 18.04.2 as far as I know. > So if you are using 18.04(.1) with kernel 4.15 this might be a problem and I > would suggest to upgrade to 18.04.2 with kernel 4.18 or later. > > Regards, > Stefan > > > > > Met vriendelijke groet/With kind regards/Mit freundlichen Grüßen, > > Berry van Sleeuwen Flight Forum 3000 5657 EW Eindhoven . +31 (0)6 > > 22564276 > > [cid:[email protected]] > > [cid:[email protected]] > > > > > > This e-mail and the documents attached are confidential and intended solely > > for the addressee; it may also be privileged. If you receive this e-mail in > > error, please notify the sender immediately and destroy it. As its > > integrity cannot be secured on the Internet, Atos' liability cannot be > > triggered for the message content. 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