Messages in this thread Patch in this message | | | From | Ricardo Neri <> | Subject | [PATCH v5 1/6] x86/sched: Decrease further the priorities of SMT siblings | Date | Fri, 10 Sep 2021 18:18:14 -0700 |
| |
When scheduling, it is better to prefer a separate physical core rather than the SMT sibling of a high priority core. The existing formula to compute priorities takes such fact in consideration. There may exist, however, combinations of priorities (i.e., maximum frequencies) in which the priority of high-numbered SMT siblings of high-priority cores collides with the priority of low-numbered SMT siblings of low-priority cores.
Consider for instance an SMT2 system with CPUs [0, 1] with priority 60 and [2, 3] with priority 30(CPUs in brackets are SMT siblings. In such a case, the resulting priorities would be [120, 60], [60, 30]. Thus, to ensure that CPU2 has higher priority than CPU1, divide the raw priority by the squared SMT iterator. The resulting priorities are [120, 30]. [60, 15].
Cc: Aubrey Li <aubrey.li@intel.com> Cc: Ben Segall <bsegall@google.com> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Quentin Perret <qperret@google.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tim Chen <tim.c.chen@linux.intel.com> Originally-by: Len Brown <len.brown@intel.com> Signed-off-by: Len Brown <len.brown@intel.com> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> --- Changes since v4: * None
Changes since v3: * Introduced this patch
Changes since v2: * N/A
Changes since v1: * N/A --- arch/x86/kernel/itmt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/itmt.c b/arch/x86/kernel/itmt.c index 1afbdd1dd777..9ff480e94511 100644 --- a/arch/x86/kernel/itmt.c +++ b/arch/x86/kernel/itmt.c @@ -198,7 +198,7 @@ void sched_set_itmt_core_prio(int prio, int core_cpu) * of the priority chain and only used when * all other high priority cpus are out of capacity. */ - smt_prio = prio * smp_num_siblings / i; + smt_prio = prio * smp_num_siblings / (i * i); per_cpu(sched_core_priority, cpu) = smt_prio; i++; } -- 2.17.1
| |