Change Config Option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE for s390x from yes to no
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
Ubuntu on IBM z Systems |
Fix Released
|
High
|
Frank Heimes | ||
linux (Ubuntu) |
Fix Released
|
Medium
|
Skipper Bug Screeners | ||
Bionic |
Fix Released
|
Medium
|
Unassigned | ||
Disco |
Fix Released
|
Medium
|
Unassigned | ||
Eoan |
Fix Released
|
Medium
|
Skipper Bug Screeners |
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-
[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_
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_
tags: | added: architecture-s39064 bugnameltc-181933 severity-high targetmilestone-inin1804 |
Changed in ubuntu: | |
assignee: | nobody → Skipper Bug Screeners (skipper-screen-team) |
affects: | ubuntu → linux (Ubuntu) |
Changed in ubuntu-z-systems: | |
status: | New → Triaged |
importance: | Undecided → High |
summary: |
- Change Config Option "CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y" -> "n" + Change Config Option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE from yes to no |
summary: |
- Change Config Option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE from yes to no + Change Config Option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE for s390x from + yes to no |
Changed in linux (Ubuntu Eoan): | |
importance: | Undecided → Medium |
Changed in linux (Ubuntu Disco): | |
importance: | Undecided → Medium |
Changed in linux (Ubuntu Bionic): | |
importance: | Undecided → Medium |
Changed in linux (Ubuntu Bionic): | |
status: | New → Fix Committed |
Changed in linux (Ubuntu Disco): | |
status: | New → Fix Committed |
Changed in linux (Ubuntu Eoan): | |
status: | In Progress → Fix Committed |
Changed in ubuntu-z-systems: | |
status: | In Progress → Fix Committed |
Changed in linux (Ubuntu): | |
status: | In Progress → Fix Committed |
Changed in ubuntu-z-systems: | |
status: | Fix Committed → Fix Released |
@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?