s390/dasd: reduce the default queue depth and nr of hardware queues
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
Ubuntu on IBM z Systems |
Fix Released
|
High
|
Frank Heimes | ||
linux (Ubuntu) |
Fix Released
|
Undecided
|
Skipper Bug Screeners | ||
Bionic |
Fix Released
|
High
|
Unassigned |
Bug Description
SRU Justification:
==================
[Impact]
* On s390x systems with a small memory footprint, but large amounts of DASD disks,
* the memory can get depleted (even during installation) which can eventually lead to a situation where the OOM kicks in (followed by even more problems).
* Starting with kernel 4.18 the patch below leads to 90% memory consumption savings per active DASD device.
* The below backport is needed to fix this and get the improvement into bionic's kernel 4.15.
[Fix]
* 3284da34a87ab7a
[Test Case]
* Configure a s390x system (z/VM guest or LPAR) with only a bit RAM, but lot's of DASDs devices.
* Now gradually enable more and more DASDs and monitor the memory usage (be sure to exclude shared memory and cache).
* One can notice a difference in mem usage of about 10:1 per activated DASD comparing the current stock 4.15 kernel with a patches kernel 4.15.
* With about less than 1GB memory and 40+ DASD devices one may start to run into an OOM situation w(o the patch.
[Regression Potential]
* The regression potential can be considered as moderate, since:
* this is purely s390x specific
* it again only affects DASD disk storage (no zFCP/SCSI disk storage)
* and it's again only limited to smaller systems (so more z/VM guests rather than LPARs).
[Other Info]
* A cherry-pick to 4.15 wasn't clean (problem in one line), hence the backport, which applied, compiled and worked fine.
__________
This fix is already available with Ubuntu 18.10, but need also be integrated into Ubuntu 18.04 LTS kernel (4.15).
This is available git-commit:
https:/
Backport information will be provided.
CVE References
tags: | added: architecture-s39064 bugnameltc-182420 severity-high targetmilestone-inin1804 |
Changed in ubuntu: | |
assignee: | nobody → Skipper Bug Screeners (skipper-screen-team) |
affects: | ubuntu → linux (Ubuntu) |
Changed in ubuntu-z-systems: | |
importance: | Undecided → High |
status: | New → Triaged |
Changed in ubuntu-z-systems: | |
assignee: | nobody → Frank Heimes (frank-heimes) |
description: | updated |
Changed in linux (Ubuntu Bionic): | |
importance: | Undecided → High |
Changed in linux (Ubuntu Bionic): | |
status: | In Progress → Fix Committed |
Changed in ubuntu-z-systems: | |
status: | In Progress → Fix Committed |
Changed in ubuntu-z-systems: | |
status: | Fix Committed → Fix Released |
------- Comment on attachment From <email address hidden> 2019-11-12 10:22 EDT-------
This is the original patch re-based on the 18.04 master-next branch. Hope this is sufficient for you.