[Kernel-packages] [Bug 1876044] Re: [UBUNTU 20.04] PSI generates overhead on s390x
--- Comment From heinz-werner_se...@de.ibm.com 2020-07-28 02:36 EDT--- IBM Bugzilla status-> closed, Fix Released with focal ** Tags removed: targetmilestone-inin--- ** Tags added: targetmilestone-inin2004 -- 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/1876044 Title: [UBUNTU 20.04] PSI generates overhead on s390x Status in Ubuntu on IBM z Systems: Fix Released Status in linux package in Ubuntu: Fix Released Status in linux source package in Focal: Fix Released Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1876044/+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 1876044] Re: [UBUNTU 20.04] PSI generates overhead on s390x
** Changed in: ubuntu-z-systems Status: Fix Committed => Fix Released -- 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/1876044 Title: [UBUNTU 20.04] PSI generates overhead on s390x Status in Ubuntu on IBM z Systems: Fix Released Status in linux package in Ubuntu: Fix Released Status in linux source package in Focal: Fix Released Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1876044/+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 1876044] Re: [UBUNTU 20.04] PSI generates overhead on s390x
This bug was fixed in the package linux - 5.4.0-42.46 --- linux (5.4.0-42.46) focal; urgency=medium * focal/linux: 5.4.0-42.46 -proposed tracker (LP: #1887069) * linux 4.15.0-109-generic network DoS regression vs -108 (LP: #1886668) - SAUCE: Revert "netprio_cgroup: Fix unlimited memory leak of v2 cgroups" linux (5.4.0-41.45) focal; urgency=medium * focal/linux: 5.4.0-41.45 -proposed tracker (LP: #1885855) * Packaging resync (LP: #1786013) - update dkms package versions * CVE-2019-19642 - kernel/relay.c: handle alloc_percpu returning NULL in relay_open * CVE-2019-16089 - SAUCE: nbd_genl_status: null check for nla_nest_start * CVE-2020-11935 - aufs: do not call i_readcount_inc() * ip_defrag.sh in net from ubuntu_kernel_selftests failed with 5.0 / 5.3 / 5.4 kernel (LP: #1826848) - selftests: net: ip_defrag: ignore EPERM * Update lockdown patches (LP: #1884159) - SAUCE: acpi: disallow loading configfs acpi tables when locked down * seccomp_bpf fails on powerpc (LP: #1885757) - SAUCE: selftests/seccomp: fix ptrace tests on powerpc * Introduce the new NVIDIA 418-server and 440-server series, and update the current NVIDIA drivers (LP: #1881137) - [packaging] add signed modules for the 418-server and the 440-server flavours -- Khalid Elmously Thu, 09 Jul 2020 19:50:26 -0400 ** Changed in: linux (Ubuntu) Status: In Progress => Fix Released ** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2019-16089 ** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2019-19642 ** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2020-11935 -- 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/1876044 Title: [UBUNTU 20.04] PSI generates overhead on s390x Status in Ubuntu on IBM z Systems: Fix Committed Status in linux package in Ubuntu: Fix Released Status in linux source package in Focal: Fix Released Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1876044/+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 1876044] Re: [UBUNTU 20.04] PSI generates overhead on s390x
This bug was fixed in the package linux - 5.4.0-37.41 --- linux (5.4.0-37.41) focal; urgency=medium * CVE-2020-0543 - SAUCE: x86/speculation/spectre_v2: Exclude Zhaoxin CPUs from SPECTRE_V2 - SAUCE: x86/cpu: Add a steppings field to struct x86_cpu_id - SAUCE: x86/cpu: Add 'table' argument to cpu_matches() - SAUCE: x86/speculation: Add Special Register Buffer Data Sampling (SRBDS) mitigation - SAUCE: x86/speculation: Add SRBDS vulnerability and mitigation documentation - SAUCE: x86/speculation: Add Ivy Bridge to affected list -- Marcelo Henrique Cerri Wed, 03 Jun 2020 11:24:23 -0300 ** Changed in: linux (Ubuntu Focal) Status: Fix Committed => Fix Released ** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2020-0543 -- 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/1876044 Title: [UBUNTU 20.04] PSI generates overhead on s390x Status in Ubuntu on IBM z Systems: Fix Committed Status in linux package in Ubuntu: In Progress Status in linux source package in Focal: Fix Released Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1876044/+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 1876044] Re: [UBUNTU 20.04] PSI generates overhead on s390x
This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- focal' to 'verification-done-focal'. If the problem still exists, change the tag 'verification-needed-focal' to 'verification-failed-focal'. If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-focal -- 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/1876044 Title: [UBUNTU 20.04] PSI generates overhead on s390x Status in Ubuntu on IBM z Systems: Fix Committed Status in linux package in Ubuntu: In Progress Status in linux source package in Focal: Fix Committed Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1876044/+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 1876044] Re: [UBUNTU 20.04] PSI generates overhead on s390x
** Changed in: ubuntu-z-systems Status: In Progress => Fix Committed -- 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/1876044 Title: [UBUNTU 20.04] PSI generates overhead on s390x Status in Ubuntu on IBM z Systems: Fix Committed Status in linux package in Ubuntu: In Progress Status in linux source package in Focal: Fix Committed Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1876044/+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 1876044] Re: [UBUNTU 20.04] PSI generates overhead on s390x
** Changed in: linux (Ubuntu Focal) Status: In Progress => Fix Committed -- 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/1876044 Title: [UBUNTU 20.04] PSI generates overhead on s390x Status in Ubuntu on IBM z Systems: In Progress Status in linux package in Ubuntu: In Progress Status in linux source package in Focal: Fix Committed Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1876044/+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 1876044] Re: [UBUNTU 20.04] PSI generates overhead on s390x
** Also affects: linux (Ubuntu Focal) Importance: Undecided Status: New ** Changed in: linux (Ubuntu Focal) Status: New => In Progress -- 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/1876044 Title: [UBUNTU 20.04] PSI generates overhead on s390x Status in Ubuntu on IBM z Systems: In Progress Status in linux package in Ubuntu: In Progress Status in linux source package in Focal: In Progress Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1876044/+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 1876044] Re: [UBUNTU 20.04] PSI generates overhead on s390x
Request submitted to kernel team's mailing list: https://lists.ubuntu.com/archives/kernel-team/2020-May/thread.html#109592 changing status to 'In Progress' ** Description changed: + 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 + 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. - + 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 - + + 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 + 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 - + no + Oops output: - no - + no + System Dump Info: - The system is not configured to capture a system dump. - - *Additional Instructions for epasch@de,ibm.com: + 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. ** Changed in: linux (Ubuntu) Status: New => In Progress ** Changed in: ubuntu-z-systems Status: Triaged => In Progress -- 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/1876044 Title: [UBUNTU 20.04] PSI generates overhead on s390x Status in Ubuntu on IBM z Systems: In Progress Status in linux package in Ubuntu: In Progress Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1876044/+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
