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Date:      Wed, 25 Sep 2019 19:29:10 +0000 (UTC)
From:      Alexander Motin <mav@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r352713 - head/sys/kern
Message-ID:  <201909251929.x8PJTA2T031248@repo.freebsd.org>
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Author: mav
Date: Wed Sep 25 19:29:09 2019
New Revision: 352713
URL: https://svnweb.freebsd.org/changeset/base/352713

Log:
  Microoptimize sched_pickcpu() after r352658.
  
  I've noticed that I missed intr check at one more SCHED_AFFINITY(),
  so instead of adding one more branching I prefer to remove few.
  
  Profiler shows the function CPU time reduction from 0.24% to 0.16%.
  
  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 19:22:03 2019	(r352712)
+++ head/sys/kern/sched_ule.c	Wed Sep 25 19:29:09 2019	(r352713)
@@ -1270,20 +1270,28 @@ sched_pickcpu(struct thread *td, int flags)
 	 */
 	if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
 	    curthread->td_intr_nesting_level) {
+		tdq = TDQ_SELF();
+		if (tdq->tdq_lowpri >= PRI_MIN_IDLE) {
+			SCHED_STAT_INC(pickcpu_idle_affinity);
+			return (self);
+		}
 		ts->ts_cpu = self;
 		intr = 1;
-	} else
+		cg = tdq->tdq_cg;
+		goto llc;
+	} else {
 		intr = 0;
+		tdq = TDQ_CPU(ts->ts_cpu);
+		cg = tdq->tdq_cg;
+	}
 	/*
 	 * If the thread can run on the last cpu and the affinity has not
 	 * expired and it is idle, run it there.
 	 */
-	tdq = TDQ_CPU(ts->ts_cpu);
-	cg = tdq->tdq_cg;
 	if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
 	    tdq->tdq_lowpri >= PRI_MIN_IDLE &&
 	    SCHED_AFFINITY(ts, CG_SHARE_L2)) {
-		if (!intr && cg->cg_flags & CG_FLAG_THREAD) {
+		if (cg->cg_flags & CG_FLAG_THREAD) {
 			CPUSET_FOREACH(cpu, cg->cg_mask) {
 				if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
 					break;
@@ -1295,6 +1303,7 @@ sched_pickcpu(struct thread *td, int flags)
 			return (ts->ts_cpu);
 		}
 	}
+llc:
 	/*
 	 * Search for the last level cache CPU group in the tree.
 	 * Skip SMT, identical groups and caches with expired affinity.

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