| 2020-04-30 07:09:22 |
bugproxy |
bug |
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added bug |
| 2020-04-30 07:09:24 |
bugproxy |
tags |
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architecture-s3903164 bugnameltc-185697 severity-medium targetmilestone-inin--- |
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| 2020-04-30 07:09:26 |
bugproxy |
ubuntu: assignee |
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Skipper Bug Screeners (skipper-screen-team) |
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| 2020-04-30 07:09:29 |
bugproxy |
affects |
ubuntu |
linux (Ubuntu) |
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| 2020-04-30 07:11:32 |
Frank Heimes |
bug task added |
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ubuntu-z-systems |
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| 2020-04-30 07:11:58 |
Frank Heimes |
linux (Ubuntu): assignee |
Skipper Bug Screeners (skipper-screen-team) |
Canonical Kernel Team (canonical-kernel-team) |
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| 2020-04-30 07:12:11 |
Frank Heimes |
ubuntu-z-systems: assignee |
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Skipper Bug Screeners (skipper-screen-team) |
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| 2020-04-30 07:12:21 |
Frank Heimes |
ubuntu-z-systems: importance |
Undecided |
Medium |
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| 2020-04-30 07:12:26 |
Frank Heimes |
ubuntu-z-systems: status |
New |
Triaged |
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| 2020-05-05 08:32:13 |
Christian Ehrhardt |
bug |
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added subscriber Christian Ehrhardt |
| 2020-05-05 18:52:45 |
Frank Heimes |
summary |
[UBUNTU 20.04] Overhead introduced by PSI |
[UBUNTU 20.04] PSI generated overhead on s390x |
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| 2020-05-05 18:52:58 |
Frank Heimes |
summary |
[UBUNTU 20.04] PSI generated overhead on s390x |
[UBUNTU 20.04] PSI generates overhead on s390x |
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| 2020-05-05 19:23:55 |
Frank Heimes |
description |
PSI is always enabled in Ubuntu 20.04.
For a test system with 72 guests on 8 cores running a nginx workload this created an overhead of ~1%.
Can we change this back to
CONFIG_PSI=y
CONFIG_PSI_DEFAULT_DISABLED=y
so that by default the overhead is not there but for debugging or if needed it can still be enabled via kernel parm?
Maybe there has been a reason for this - so feel free to discuss.
---uname output---
Linux t35lp76 5.4.0-26-generic #30-Ubuntu SMP Mon Apr 20 16:57:22 UTC 2020 s390x s390x s390x GNU/Linux
Machine Type = All s390x architecture
---Debugger---
A debugger is not configured
---Steps to Reproduce---
root@t35lp76:/boot# grep PSI config-5.4.0-26-generic
CONFIG_PSI=y
# CONFIG_PSI_DEFAULT_DISABLED is not set
Stack trace output:
no
Oops output:
no
System Dump Info:
The system is not configured to capture a system dump.
*Additional Instructions for epasch@de,ibm.com:
-Attach sysctl -a output output to the bug. |
SRU Justification:
==================
[Impact]
* PSI is enabled by default for all architectures in Ubuntu.
* On s390x this leads to performance degradations on popular workloads like web serving (nginx).
[Fix]
* Leave 'CONFIG_PSI=y', but change 'CONFIG_PSI_DEFAULT_DISABLED=n' to 'CONFIG_PSI_DEFAULT_DISABLED=y'
[Test Case]
* Measure the overhead with 'CONFIG_PSI_DEFAULT_DISABLED=n' and 'CONFIG_PSI_DEFAULT_DISABLED=y' on the same environment with nginx.
[Regression Potential]
* The regression potential can be considered as moderate, since PSI (Pressure stall information tracking),
* since PSI is just used to collect CPU overcommitted, memory and IO metrics.
* And it can be enabled again with the kernel argument.
__________
PSI is always enabled in Ubuntu 20.04.
For a test system with 72 guests on 8 cores running a nginx workload this created an overhead of ~1%.
Can we change this back to
CONFIG_PSI=y
CONFIG_PSI_DEFAULT_DISABLED=y
so that by default the overhead is not there but for debugging or if needed it can still be enabled via kernel parm?
Maybe there has been a reason for this - so feel free to discuss.
---uname output---
Linux t35lp76 5.4.0-26-generic #30-Ubuntu SMP Mon Apr 20 16:57:22 UTC 2020 s390x s390x s390x GNU/Linux
Machine Type = All s390x architecture
---Debugger---
A debugger is not configured
---Steps to Reproduce---
root@t35lp76:/boot# grep PSI config-5.4.0-26-generic
CONFIG_PSI=y
# CONFIG_PSI_DEFAULT_DISABLED is not set
Stack trace output:
no
Oops output:
no
System Dump Info:
The system is not configured to capture a system dump.
*Additional Instructions for epasch@de,ibm.com:
-Attach sysctl -a output output to the bug. |
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| 2020-05-05 19:24:56 |
Frank Heimes |
linux (Ubuntu): status |
New |
In Progress |
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| 2020-05-05 19:25:01 |
Frank Heimes |
ubuntu-z-systems: status |
Triaged |
In Progress |
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| 2020-05-13 09:06:45 |
Kleber Sacilotto de Souza |
nominated for series |
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Ubuntu Focal |
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| 2020-05-13 09:06:45 |
Kleber Sacilotto de Souza |
bug task added |
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linux (Ubuntu Focal) |
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| 2020-05-13 09:06:53 |
Kleber Sacilotto de Souza |
linux (Ubuntu Focal): status |
New |
In Progress |
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| 2020-05-15 09:53:15 |
Kleber Sacilotto de Souza |
linux (Ubuntu Focal): status |
In Progress |
Fix Committed |
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| 2020-05-15 10:02:13 |
Frank Heimes |
ubuntu-z-systems: status |
In Progress |
Fix Committed |
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| 2020-05-19 14:32:53 |
Ubuntu Kernel Bot |
tags |
architecture-s3903164 bugnameltc-185697 severity-medium targetmilestone-inin--- |
architecture-s3903164 bugnameltc-185697 severity-medium targetmilestone-inin--- verification-needed-focal |
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| 2020-06-09 21:04:04 |
Launchpad Janitor |
linux (Ubuntu Focal): status |
Fix Committed |
Fix Released |
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| 2020-06-09 21:04:04 |
Launchpad Janitor |
cve linked |
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2020-0543 |
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| 2020-07-28 00:57:39 |
Launchpad Janitor |
linux (Ubuntu): status |
In Progress |
Fix Released |
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| 2020-07-28 00:57:39 |
Launchpad Janitor |
cve linked |
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2019-16089 |
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| 2020-07-28 00:57:39 |
Launchpad Janitor |
cve linked |
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2019-19642 |
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| 2020-07-28 00:57:39 |
Launchpad Janitor |
cve linked |
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2020-11935 |
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| 2020-07-28 05:50:05 |
Frank Heimes |
ubuntu-z-systems: status |
Fix Committed |
Fix Released |
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| 2020-07-28 06:39:46 |
bugproxy |
tags |
architecture-s3903164 bugnameltc-185697 severity-medium targetmilestone-inin--- verification-needed-focal |
architecture-s3903164 bugnameltc-185697 severity-medium targetmilestone-inin2004 verification-needed-focal |
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