[Kernel-packages] [Bug 1848492] Comment bridged from LTC Bugzilla
--- Comment From heinz-werner_se...@de.ibm.com 2020-01-07 08:58 EDT--- IBM bugzilla status-> closed, fix Released with requested distros -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1848492 Title: Change Config Option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE for s390x from yes to no Status in Ubuntu on IBM z Systems: Fix Released Status in linux package in Ubuntu: Fix Released Status in linux source package in Bionic: Fix Released Status in linux source package in Disco: Fix Released Status in linux source package in Eoan: Fix Released Bug description: SRU Justification: == [Impact] * By default all standby memory that is configured to an LPAR is used at boot (IPL) time. * But the standby memory is meant to be added and used on demand later (after IPL). [Fix] * 0001-Ubuntu-Config-Disabled-CONFIG_MEMORY_HOTPLUG_DEFAULT.patch [Test Case] * Configure an LPAR in it's Activation Profile with a certain amount of 'Initial' memory and some 'Reserved' memory on top. * Re-activate the LPAR to make the changes take effect and boot (IPL) Ubuntu. * Check with the help of free whether the reported memory is only the initial memory (actual) or initial+reserved (desired). [Regression Potential] * There is a certain regression potential, since some systems may have Initial and Reserved memory already defined today and have it already all in use under Linux (today obviously w/o having it dynamically added). * If such a system got re-activated and rebooted, the memory size will then be what's defined as Initial memory and no longer Initial+Reserved. * To be able to use the same size of the memory than before, the Reserved memory need to be either dynamically be added or the Initial memory re-configured to the sum of former Initial+Reserved. * The latter case requires a re-activation of the LPAR, but since this corner case only happens after a reboot, a downtime is already in place for the re-activation. * But overall the regression potential is low since it's for s390x only and the 'Reserved' memory option in the Activation Profile is rarely used. [Other Info] * In the past this config option was diabled for ppc64el, too. __ The Ubuntu kernel configuration contains CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y for s390. This causes all standby memory configured for an LPAR to be used at IPL time. Note that this is definetaly not what a user wants on s390. The normal process is: define a certain amount of "base" memory which the system should use when IPL'ed, and define also a certain amount of "standby" memory which can be (also only partially) be additionaly used when necessary. Also note that it is *not* possible to add additional memory to a runnung system, besides the amount of memory specified as "standby". Therefore please change the kernel config option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE to "n" for s390. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1848492/+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
[Kernel-packages] [Bug 1848492] Comment bridged from LTC Bugzilla
--- Comment From h.carst...@de.ibm.com 2019-10-17 09:58 EDT--- (In reply to comment #7) > @IBM: For a kernel SRU request we would need a test case. > Since the terminology between Linux, HMC in DPM mode and HMC in classic mode > is different, > am I right assuming that we talk (in terms of classic mode, that's what we > have) about: > Activation Profile --> Storage > and then > Central Storage: > Initial n GB > and > Reserved m GB > and after a re-activation of the LPAR, incl. IPL, free must only show n GB, > right? Yes, that's correct. We are talking about the "Reserved" field with "Central Storage". I wouldn't know how to write a test case here, since the kernel brought up all "reserved"/"standby" memory already before user space can figure out anything. The only thing that works: _if_ you know that an LPAR is configured with "Reserved" memory then the last line of the output of lsmem must _not_ look this: Total offline memory: 0B But instead contain a value that is not zero. We may play some tricks about to which (Linux) memory zone got added, but that changed in the past - and I really wouldn't rely on that for a test case. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1848492 Title: Change Config Option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE from yes to no Status in Ubuntu on IBM z Systems: Triaged Status in linux package in Ubuntu: New Bug description: The Ubuntu kernel configuration contains CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y for s390. This causes all standby memory configured for an LPAR to be used at IPL time. Note that this is definetaly not what a user wants on s390. The normal process is: define a certain amount of "base" memory which the system should use when IPL'ed, and define also a certain amount of "standby" memory which can be (also only partially) be additionaly used when necessary. Also note that it is *not* possible to add additional memory to a runnung system, besides the amount of memory specified as "standby". Therefore please change the kernel config option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE to "n" for s390. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1848492/+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
