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Date:      Thu, 30 Nov 2017 01:40:07 +0000 (UTC)
From:      Jung-uk Kim <jkim@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r326383 - head/sys/x86/cpufreq
Message-ID:  <201711300140.vAU1e7dC001292@repo.freebsd.org>
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Author: jkim
Date: Thu Nov 30 01:40:07 2017
New Revision: 326383
URL: https://svnweb.freebsd.org/changeset/base/326383

Log:
  Add a tunable "debug.hwpstate_verify" to check P-state after changing it and
  turn it off by default.  It is very inefficient to verify current P-state of
  each core, especially for CPUs with many cores.  When multiple commands are
  requested to the same power domain before completion of pending transitions,
  the last command is executed according to the manual.  Because requests are
  serialized by the caller, all cores will receive the same command for each
  call.  Do not call sched_bind() and sched_unbind().  It is redundant because
  the caller does it anyway.

Modified:
  head/sys/x86/cpufreq/hwpstate.c

Modified: head/sys/x86/cpufreq/hwpstate.c
==============================================================================
--- head/sys/x86/cpufreq/hwpstate.c	Thu Nov 30 00:27:49 2017	(r326382)
+++ head/sys/x86/cpufreq/hwpstate.c	Thu Nov 30 01:40:07 2017	(r326383)
@@ -123,10 +123,14 @@ static int	hwpstate_get_info_from_acpi_perf(device_t d
 static int	hwpstate_get_info_from_msr(device_t dev);
 static int	hwpstate_goto_pstate(device_t dev, int pstate_id);
 
-static int	hwpstate_verbose = 0;
+static int	hwpstate_verbose;
 SYSCTL_INT(_debug, OID_AUTO, hwpstate_verbose, CTLFLAG_RWTUN,
     &hwpstate_verbose, 0, "Debug hwpstate");
 
+static int	hwpstate_verify;
+SYSCTL_INT(_debug, OID_AUTO, hwpstate_verify, CTLFLAG_RWTUN,
+    &hwpstate_verify, 0, "Verify P-state after setting");
+
 static device_method_t hwpstate_methods[] = {
 	/* Device interface */
 	DEVMETHOD(device_identify,	hwpstate_identify),
@@ -160,15 +164,13 @@ DRIVER_MODULE(hwpstate, cpu, hwpstate_driver, hwpstate
  * Go to Px-state on all cpus considering the limit.
  */
 static int
-hwpstate_goto_pstate(device_t dev, int pstate)
+hwpstate_goto_pstate(device_t dev, int id)
 {
 	sbintime_t sbt;
 	int i;
 	uint64_t msr;
 	int j;
 	int limit;
-	int id = pstate;
-	int error;
 
 	/* get the current pstate limit */
 	msr = rdmsr(MSR_AMD_10H_11H_LIMIT);
@@ -176,47 +178,57 @@ hwpstate_goto_pstate(device_t dev, int pstate)
 	if (limit > id)
 		id = limit;
 
+	HWPSTATE_DEBUG(dev, "setting P%d-state on cpu%d\n", id,
+	    PCPU_GET(cpuid));
+	/* Go To Px-state */
+	wrmsr(MSR_AMD_10H_11H_CONTROL, id);
+
 	/*
 	 * We are going to the same Px-state on all cpus.
 	 * Probably should take _PSD into account.
 	 */
-	error = 0;
 	CPU_FOREACH(i) {
+		if (i == PCPU_GET(cpuid))
+			continue;
+
 		/* Bind to each cpu. */
 		thread_lock(curthread);
 		sched_bind(curthread, i);
 		thread_unlock(curthread);
-		HWPSTATE_DEBUG(dev, "setting P%d-state on cpu%d\n",
-		    id, PCPU_GET(cpuid));
+		HWPSTATE_DEBUG(dev, "setting P%d-state on cpu%d\n", id, i);
 		/* Go To Px-state */
 		wrmsr(MSR_AMD_10H_11H_CONTROL, id);
 	}
-	CPU_FOREACH(i) {
-		/* Bind to each cpu. */
-		thread_lock(curthread);
-		sched_bind(curthread, i);
-		thread_unlock(curthread);
-		/* wait loop (100*100 usec is enough ?) */
-		for (j = 0; j < 100; j++) {
-			/* get the result. not assure msr=id */
-			msr = rdmsr(MSR_AMD_10H_11H_STATUS);
-			if (msr == id)
-				break;
-			sbt = SBT_1MS / 10;
-			tsleep_sbt(dev, PZERO, "pstate_goto", sbt,
-			    sbt >> tc_precexp, 0);
+
+	/*
+	 * Verify whether each core is in the requested P-state.
+	 */
+	if (hwpstate_verify) {
+		CPU_FOREACH(i) {
+			thread_lock(curthread);
+			sched_bind(curthread, i);
+			thread_unlock(curthread);
+			/* wait loop (100*100 usec is enough ?) */
+			for (j = 0; j < 100; j++) {
+				/* get the result. not assure msr=id */
+				msr = rdmsr(MSR_AMD_10H_11H_STATUS);
+				if (msr == id)
+					break;
+				sbt = SBT_1MS / 10;
+				tsleep_sbt(dev, PZERO, "pstate_goto", sbt,
+				    sbt >> tc_precexp, 0);
+			}
+			HWPSTATE_DEBUG(dev, "result: P%d-state on cpu%d\n",
+			    (int)msr, i);
+			if (msr != id) {
+				HWPSTATE_DEBUG(dev,
+				    "error: loop is not enough.\n");
+				return (ENXIO);
+			}
 		}
-		HWPSTATE_DEBUG(dev, "result: P%d-state on cpu%d\n",
-		    (int)msr, PCPU_GET(cpuid));
-		if (msr != id) {
-			HWPSTATE_DEBUG(dev, "error: loop is not enough.\n");
-			error = ENXIO;
-		}
 	}
-	thread_lock(curthread);
-	sched_unbind(curthread);
-	thread_unlock(curthread);
-	return (error);
+
+	return (0);
 }
 
 static int

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