ACK/Cmnt: [SRU][F][PATCH 1/1] Ubuntu: [Config] CONFIG_PSI is enabled by default, but creates additional overhead on s390x, hence should be disabled by default on s390x only.

[Frank Heimes]

Okay, so the following two lines are needed ?!
CONFIG_PSI_DEFAULT_DISABLED                     note<LP:1876044>
CONFIG_PSI_DEFAULT_DISABLED                     mark<ENFORCE>
(maybe one line with a 'tab' beween note... and mark...)

Btw. is there some documentation (wiki or so) that explains these? Since
I'm struggleing a bit and mainly just compare here with other settings ...

Would this change be doable by the kernel team 'on the fly' - or do you
need a "v2" (could be quite difficult since today is already last day for
commit ...)

BR, Frank

On Wed, May 13, 2020 at 9:09 PM Seth Forshee <seth.forshee at canonical.com>
wrote:

> On Wed, May 13, 2020 at 11:17:07AM +0200, Stefan Bader wrote:
> > On 05.05.20 21:20, frank.heimes at canonical.com wrote:
> > > From: Frank Heimes <frank.heimes at canonical.com>
> > >
> > > BugLink: https://bugs.launchpad.net/bugs/1876044
> > >
> > > PSI is always enabled in Ubuntu due to 'CONFIG_PSI_DEFAULT_DISABLED=n'
> / 'not set'.
> > > This causes a performance degradation for popular workloads like web
> serving (nginx) due to additional overhead.
> > > Hence IBM is requesting to change this option to yes for s390x:
> 'CONFIG_PSI_DEFAULT_DISABLED=y'.
> > > CONFIG_PSI is already set to yes, and should stay.
> > >
> > > Signed-off-by: Frank Heimes <frank.heimes at canonical.com>
> > Acked-by: Stefan Bader <stefan.bader at canonical.com>
> > > ---
> >
> > I would not know of any reason and nobody spoke up so far. I guess this
> option
> > is only relevant for s390x and therefor enforcing the change there makes
> the
> > config change go into the common file. Andy, is there a better way to
> record a
> > don't care for other arches in the annotations file? Like 'amd64': '-'.
>
> Do you mean by this that you want something that would enforce the value
> for only s390x without enforcing it for other architectures? I don't
> think '-' would work for this, because iirc that says that the option is
> not selectable, and the enforcer will not treat it as equal to 'n'.
>
> >
> > -Stefan
> >
> > >  debian.master/config/annotations          | 4 +++-
> > >  debian.master/config/config.common.ubuntu | 2 +-
> > >  2 files changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/debian.master/config/annotations
> b/debian.master/config/annotations
> > > index dd6481141e9f..20fd9e21bc72 100644
> > > --- a/debian.master/config/annotations
> > > +++ b/debian.master/config/annotations
> > > @@ -10316,7 +10316,9 @@ CONFIG_TASK_DELAY_ACCT
>   policy<{'amd64': 'y', 'arm64': '
> > >  CONFIG_TASK_XACCT                               policy<{'amd64': 'y',
> 'arm64': 'y', 'armhf': 'y', 'i386': 'y', 'ppc64el': 'y', 's390x': 'y'}>
> > >  CONFIG_TASK_IO_ACCOUNTING                       policy<{'amd64': 'y',
> 'arm64': 'y', 'armhf': 'y', 'i386': 'y', 'ppc64el': 'y', 's390x': 'y'}>
> > >  CONFIG_PSI                                      policy<{'amd64': 'y',
> 'arm64': 'y', 'armhf': 'y', 'i386': 'y', 'ppc64el': 'y', 's390x': 'y'}>
> > > -CONFIG_PSI_DEFAULT_DISABLED                     policy<{'amd64': 'n',
> 'arm64': 'n', 'armhf': 'n', 'i386': 'n', 'ppc64el': 'n', 's390x': 'n'}>
> > > +CONFIG_PSI_DEFAULT_DISABLED                     policy<{'amd64': 'n',
> 'arm64': 'n', 'armhf': 'n', 'i386': 'n', 'ppc64el': 'n', 's390x': 'y'}>
> > > +
> > > +CONFIG_PSI_DEFAULT_DISABLED                     mark<LP:1876044>
>
> This is wrong, but numbers should be recorded in note<> annotations. I
> would think we would also want mark<ENFORCE> here.
>
> > >
> > >  # Menu: General setup >> CPU/Task time and stats accounting >>
> Cputime accounting
> > >  CONFIG_TICK_CPU_ACCOUNTING                      policy<{'amd64': 'y',
> 'arm64': 'y', 'armhf': 'y', 'i386': 'y', 'ppc64el': 'y', }>
> > > diff --git a/debian.master/config/config.common.ubuntu
> b/debian.master/config/config.common.ubuntu
> > > index f502f2bdfa07..115590e89d73 100644
> > > --- a/debian.master/config/config.common.ubuntu
> > > +++ b/debian.master/config/config.common.ubuntu
> > > @@ -7567,7 +7567,7 @@ CONFIG_PSAMPLE=m
> > >  CONFIG_PSERIES_CPUIDLE=y
> > >  CONFIG_PSERIES_ENERGY=m
> > >  CONFIG_PSI=y
> > > -# CONFIG_PSI_DEFAULT_DISABLED is not set
> > > +CONFIG_PSI_DEFAULT_DISABLED=y
> > >  # CONFIG_PSTORE_842_COMPRESS is not set
> > >  CONFIG_PSTORE_COMPRESS=y
> > >  CONFIG_PSTORE_COMPRESS_DEFAULT="deflate"
> > >
> >
> >
>
>
>
>
> > --
> > kernel-team mailing list
> > kernel-team at lists.ubuntu.com
> > https://lists.ubuntu.com/mailman/listinfo/kernel-team
>
>
> --
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team
>
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