Re: [patch 1/4] add basic task isolation prctl interface

Marcelo Tosatti
2021-07-28T17:04:01Z

On Wed, Jul 28, 2021 at 11:00:01AM -0400, Nitesh Lal wrote:
> > > A latency sensitive
> > > application might be OK with the former but not with the latter.
> >
> > Two alternatives:
> >
> > 1) The pattern above, where particular subsystems that might interrupt
> > the kernel are enabled automatically if the kernel supports it.
> >
> > Pros:
> > Applications which implement this only need to be changed once,
> > and can benefit from new kernel features.
> >
> > Applications can disable particular features if they turn
> > out to be problematic.
> >
> > Cons:
> > New features might break applications.
> >
> > 2) Force applications to enable each new feature individually.
> >
> > Pros: Won't cause regressions, kernel behaviour is explicitly
> > controlled by userspace.
> >
> > Cons: Apps won't benefit from new features automatically.
> >
> > ---
> >
> > It seems to me 1) is preferred. Can also add a sysfs control to
> > have a "default_isolation_feature" flag, which can be changed
> > by a sysadmin in case a new feature is undesired.
> >
> > Thoughts?
> >
> >
> The first option may work specifically with the sysfs interface that you
> mentioned, however, IMHO (2) is safer than regressing the workloads. Also,
> if the previously implemented controls are good enough for the workload
> then there should not be a need to enable the new ones.

OK, can set default_isolation_feature as 0 then, which admin can
configure to a non-default value. This would enable the new
features only if the admin enables them.

Thanks.