lkml.org 
[lkml]   [2020]   [Nov]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 4.19 156/191] powerpc: Warn about use of smt_snooze_delay
On Thu, 5 Nov 2020 at 19:24, Pavel Machek <pavel@ucw.cz> wrote:
>
> Hi!
>
> > From: Joel Stanley <joel@jms.id.au>
> >
> > commit a02f6d42357acf6e5de6ffc728e6e77faf3ad217 upstream.
> >
> > It's not done anything for a long time. Save the percpu variable, and
> > emit a warning to remind users to not expect it to do anything.
> >
> > This uses pr_warn_once instead of pr_warn_ratelimit as testing
> > 'ppc64_cpu --smt=off' on a 24 core / 4 SMT system showed the warning
> > to be noisy, as the online/offline loop is slow.
>
> I don't believe this is good idea for stable. It is in 5.9-rc2, and
> likely mainline users will get userspace fixed, but that warning is
> less useful for -stable users.

The warning is about the existing behaviour of the kernel. It does let
the user know that they won't see any difference in behaviour when
tweaking the smt_snooze_delay variable, which was a real issue that
Anton hit.

I agree that the future commit that removes smt_snooze_delay from the
kernel should not be backported.

Cheers,

Joel

>
> (And besides, it does not fix any serious bug).
>
> Best regards,
> Pavel
>
> --
> http://www.livejournal.com/~pavelmachek

\
 
 \ /
  Last update: 2020-11-06 00:45    [W:0.242 / U:0.212 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site