@@ -2461,4 +2461,6 @@ static inline void sched_core_fork(struct task_struct *p) { }
extern void sched_set_stop_task(int cpu, struct task_struct *stop);
+extern bool sched_smt_siblings_idle(int cpu);
+
#endif
@@ -1064,7 +1064,14 @@ update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
* Scheduling class queueing methods:
*/
-static inline bool is_core_idle(int cpu)
+/**
+ * sched_smt_siblings_idle - Check whether SMT siblings of a CPU are idle
+ * @cpu: The CPU to check
+ *
+ * Returns true if all the SMT siblings of @cpu are idle or @cpu does not have
+ * SMT siblings. The idle state of @cpu is not considered.
+ */
+bool sched_smt_siblings_idle(int cpu)
{
#ifdef CONFIG_SCHED_SMT
int sibling;
@@ -1767,7 +1774,7 @@ static inline int numa_idle_core(int idle_core, int cpu)
* Prefer cores instead of packing HT siblings
* and triggering future load balancing.
*/
- if (is_core_idle(cpu))
+ if (sched_smt_siblings_idle(cpu))
idle_core = cpu;
return idle_core;
@@ -9652,7 +9659,7 @@ static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
if (!sched_smt_active())
return true;
- return sd->flags & SD_SHARE_CPUCAPACITY || is_core_idle(cpu);
+ return sd->flags & SD_SHARE_CPUCAPACITY || sched_smt_siblings_idle(cpu);
}
/**
X86 needs to know the idle state of the SMT siblings of a CPU to improve the accuracy of IPCC classification. X86 implements support for IPC classes in the thermal HFI driver. Rename is_core_idle() as sched_smt_siblings_idle() and make it available outside the scheduler code. Cc: Ben Segall <bsegall@google.com> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Len Brown <len.brown@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Perry Yuan <Perry.Yuan@amd.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 C. Chen <tim.c.chen@intel.com> Cc: Valentin Schneider <vschneid@redhat.com> Cc: Zhao Liu <zhao1.liu@linux.intel.com> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> --- is_core_idle() is no longer an inline function after this patch. To rule out performance degradation, I compared the execution time of the inline and non-inline versions on a 4-socket Cascade Lake system using the NUMA stressor of stress-ng. I used this test command: $ stress-ng --numa 1500 -t 10m During the test, is_core_idle() was called ~200,000 times. To measure the execution time, I recorded the value of the TSC counter before and after calling is_core_idle() and calculated the difference. value. I arbitrarily removed outliers (defined as any delta larger than 5000 counts). This required removing ~40 samples. The table below summarizes the difference in execution time. All values are expressed in TSC counts, except for the standard deviation, expressed as a percentage of the average. Average Median Std(%) Mode TSCdelta inline 668.76 626 67.24 42 TSCdelta non-inline 677.64 624 67.67 46 The metrics show that both the inline and non-inline versions exhibit similar performance characteristics. --- Changes since v3: * None Changes since v2: * Brought back this previously dropped patch. * Profiled inline vs non-inline is_core_idle(). I found not major penalty. * Merged is_core_idle() and sched_smt_siblings_idle() into a single function. (Dietmar) Changes since v1: * Dropped this patch. --- include/linux/sched.h | 2 ++ kernel/sched/fair.c | 13 ++++++++++--- 2 files changed, 12 insertions(+), 3 deletions(-)