Author: mav Date: Thu Sep 26 00:35:06 2019 New Revision: 352728 URL: https://svnweb.freebsd.org/changeset/base/352728
Log: Microoptimize sched_pickcpu() CPU affinity on SMT. Use of CPU_FFS() to implement CPUSET_FOREACH() allows to save up to ~0.5% of CPU time on 72-thread SMT system doing 80K IOPS to NVMe from one thread. MFC after: 1 month Sponsored by: iXsystems, Inc. Modified: head/sys/kern/sched_ule.c Modified: head/sys/kern/sched_ule.c ============================================================================== --- head/sys/kern/sched_ule.c Wed Sep 25 22:53:30 2019 (r352727) +++ head/sys/kern/sched_ule.c Thu Sep 26 00:35:06 2019 (r352728) @@ -643,10 +643,6 @@ struct cpu_search { #define CPU_SEARCH_HIGHEST 0x2 #define CPU_SEARCH_BOTH (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST) -#define CPUSET_FOREACH(cpu, mask) \ - for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++) \ - if (CPU_ISSET(cpu, &mask)) - static __always_inline int cpu_search(const struct cpu_group *cg, struct cpu_search *low, struct cpu_search *high, const int match); int __noinline cpu_search_lowest(const struct cpu_group *cg, @@ -1292,13 +1288,17 @@ sched_pickcpu(struct thread *td, int flags) tdq->tdq_lowpri >= PRI_MIN_IDLE && SCHED_AFFINITY(ts, CG_SHARE_L2)) { if (cg->cg_flags & CG_FLAG_THREAD) { - CPUSET_FOREACH(cpu, cg->cg_mask) { - if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE) + /* Check all SMT threads for being idle. */ + for (cpu = CPU_FFS(&cg->cg_mask) - 1; ; cpu++) { + if (CPU_ISSET(cpu, &cg->cg_mask) && + TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE) break; + if (cpu >= mp_maxid) { + SCHED_STAT_INC(pickcpu_idle_affinity); + return (ts->ts_cpu); + } } - } else - cpu = INT_MAX; - if (cpu > mp_maxid) { + } else { SCHED_STAT_INC(pickcpu_idle_affinity); return (ts->ts_cpu); } _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"