* Shrikanth Hegde <[email protected]> [2026-10-12 15:50:34]: Hi Shrikanth,
> > As a result, it may be enabled but has no room to operate. > Hence provide a debugfs option one can set to try experiment their > workload with cache aware scheduling. This also provides ways to explore > it on system with SMT=4 to see if there are any opportunities > to improve or uncover bugs if there is any. > > This does not change the hardware cache topology. It only changes the > sched-domain level at which SD_SHARE_LLC is set. > > Initially start with, > - New debugs file called llc_override. It can be set/get on > /sys/kernel/debug/powerpc/llc_override > - Adds parser logic for the debug knob. > This is a good way to allow experimenting to know if a software override of the LLC esp given the latency numbers within hemisphere and chip. > There is no point in setting NUMA as the LLC domain. So give option > until pkg to experiment with. > > Actual flag manipulations and rebuilding sched domains are introduced > in subsequent patches. > > Signed-off-by: Shrikanth Hegde <[email protected]> > --- > PS: Split is deliberate. If squashing all this into one patch helps, > let me know. > > arch/powerpc/kernel/smp.c | 90 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 90 insertions(+) > > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c > index 6a5a5469aaae..433757511adb 100644 > --- a/arch/powerpc/kernel/smp.c > +++ b/arch/powerpc/kernel/smp.c > @@ -36,6 +36,7 @@ > #include <linux/pgtable.h> > #include <linux/clockchips.h> > #include <linux/kexec.h> > +#include <linux/debugfs.h> > > #include <asm/ptrace.h> > #include <linux/atomic.h> > @@ -1826,3 +1827,92 @@ void __noreturn arch_cpu_idle_dead(void) > } > > #endif > + > +enum llc_override_values { > + LLC_OVERRIDE_DISABLED, > + LLC_OVERRIDE_SMT, > + LLC_OVERRIDE_MC, > + LLC_OVERRIDE_PKG, > +}; > + For the current experiments, would it help to keep it simple and have just SMT and MC. I mean we can include disabled and pkg based on our experiments. -- Thanks and Regards Srikar Dronamraju
