Messages in this thread | | | From | Joel Fernandes <> | Date | Mon, 24 May 2021 16:50:43 -0400 | Subject | Re: config SCHED_CORE |
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On Fri, May 21, 2021 at 9:36 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Fri, May 21, 2021 at 07:57:35AM -0400, Joel Fernandes wrote: > > > > --- > > > kernel/Kconfig.preempt | 14 +++++++++++++- > > > 1 file changed, 13 insertions(+), 1 deletion(-) > > > > > > diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt > > > index ea1e3331c0ba..3c4566cd20ef 100644 > > > --- a/kernel/Kconfig.preempt > > > +++ b/kernel/Kconfig.preempt > > > @@ -104,4 +104,16 @@ config SCHED_CORE > > > bool "Core Scheduling for SMT" > > > default y > > > depends on SCHED_SMT > > > - > > > + help > > > + This option enables Core scheduling, a means of coordinated task > > > + selection across SMT siblings with the express purpose of creating a > > > + Core wide privilidge boundary. When enabled -- see prctl(PR_SCHED_CORE) > > > + -- task selection will ensure all SMT siblings will execute a task > > > + from the same 'core group', forcing idle when no matching task is found. > > > + > > > + This provides means of mitigation against a number of SMT side-channels; > > > + but is, on its own, insufficient to mitigate all known side-channels. > > > + Notable: the MDS class of attacks require more. > > > + > > > + Default enabled for anything that has SCHED_SMT, when unused there should > > > + be no impact on performance. > > > > This description sort of makes it sound like security is the only > > usecase. Perhaps we can also add here that core-scheduling can help > > performance of workloads where hyperthreading is undesired, such as > > when VM providers don't want to share hyperthreads. > > > > Thoughts? > > You're right. And there's this whole class of people who want to use > this to eliminate SMT interference.
That's good, even more core scheduling users ;-)
> I'll see if I can work that in > without turning the whole thing into a novella or so ;-/
Your patch looked good to me (delta Randy/Hugh's comments). I still owe you the documentation patch refresh, I'll send it out soon. Thanks,
- Joel
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