kernel & libbsd.so: add getloadavg() and _user_get_loadavg()

the algorithm and reference values are from FreeBSD.

Change-Id: Ia74a796e13adce6a70434c7546c25ca3d553f11f
Reviewed-on: https://review.haiku-os.org/c/haiku/+/9150
Reviewed-by: waddlesplash <[email protected]>
Reviewed-by: Jérôme Duval <[email protected]>
Tested-by: Commit checker robot <[email protected]>

headers/compatibility/bsd/stdlib.h

@@ -30,6 +30,8 @@ int			mkstemps(char *templat, int slen);
 long long	strtonum(const char *numstr, long long minval,
 				long long maxval, const char **errstrp);
 
+int			getloadavg(double array[], int size);
+
 #ifdef __cplusplus
 }
 #endif

headers/private/kernel/kscheduler.h

@@ -85,6 +85,7 @@ void scheduler_add_listener(struct SchedulerListener* listener);
 void scheduler_remove_listener(struct SchedulerListener* listener);
 
 void scheduler_init(void);
+status_t scheduler_loadavg_init();
 void scheduler_enable_scheduling(void);
 void scheduler_update_policy(void);
 
@@ -95,6 +96,9 @@ status_t _user_analyze_scheduling(bigtime_t from, bigtime_t until, void* buffer,
 status_t _user_set_scheduler_mode(int32 mode);
 int32 _user_get_scheduler_mode(void);
 
+status_t _user_get_loadavg(struct loadavg* info, size_t size);
+
+
 #ifdef __cplusplus
 }
 #endif

headers/private/system/scheduler_defs.h

@@ -62,4 +62,10 @@ struct scheduling_analysis {
 };
 
 
+struct loadavg {
+	uint32	ldavg[3];
+	long 	fscale;
+};
+
+
 #endif	/* _SYSTEM_SCHEDULER_DEFS_H */

headers/private/system/syscalls.h

@@ -28,6 +28,7 @@ struct fd_info;
 struct fd_set;
 struct fs_info;
 struct iovec;
+struct loadavg;
 struct msqid_ds;
 struct net_stat;
 struct pollfd;
@@ -212,6 +213,7 @@ extern bigtime_t	_kern_estimate_max_scheduling_latency(thread_id thread);
 
 extern status_t		_kern_set_scheduler_mode(int32 mode);
 extern int32		_kern_get_scheduler_mode(void);
+extern status_t		_kern_get_loadavg(struct loadavg* info, size_t size);
 
 // user/group functions
 extern gid_t		_kern_getgid(bool effective);

src/libs/bsd/Jamfile

@@ -19,6 +19,7 @@ for architectureObject in [ MultiArchSubDirSetup ] {
 			explicit_bzero.c
 			fgetln.c
 			fts.c
+			getloadavg.cpp
 			getpass.c
 			issetugid.c
 			kqueue.cpp

src/libs/bsd/getloadavg.cpp

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2025, Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ */
+
+
+#include <stdlib.h>
+
+#include <scheduler_defs.h>
+#include <syscalls.h>
+
+
+extern "C" int
+getloadavg(double loadavg[], int count)
+{
+	struct loadavg info;
+
+	if (_kern_get_loadavg(&info, sizeof(info)) != B_OK)
+		return -1;
+
+	size_t size = min_c((size_t)count, B_COUNT_OF(info.ldavg));
+	for (size_t i = 0; i < size; i++)
+		loadavg[i] = (double)info.ldavg[i] / info.fscale;
+	return count;
+}

src/system/kernel/Jamfile

@@ -70,6 +70,7 @@ KernelMergeObject kernel_core.o :
 	power_saving.cpp
 	scheduler.cpp
 	scheduler_cpu.cpp
+	scheduler_load.cpp
 	scheduler_profiler.cpp
 	scheduler_thread.cpp
 	scheduler_tracing.cpp

src/system/kernel/main.cpp

@@ -313,6 +313,8 @@ main2(void* /*unused*/)
 	TRACE("init system notifications\n");
 	system_notifications_init();
 
+	scheduler_loadavg_init();
+
 	TRACE("Init modules\n");
 	boot_splash_set_stage(BOOT_SPLASH_STAGE_1_INIT_MODULES);
 	module_init_post_threads();

src/system/kernel/scheduler/scheduler_load.cpp

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2025, Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT license.
+ */
+
+
+#include "scheduler_cpu.h"
+
+#include <kernel.h>
+#include <scheduler_defs.h>
+
+
+using namespace Scheduler;
+
+// load average algorithm from FreeBSD, see kern_sync.c
+const static int kFShift = 11;
+const static long kFScale = 1 << kFShift;
+static struct loadavg sAverageRunnable = {{0, 0, 0}, kFScale};
+const static uint64 sCExp[3] = {(uint64)(0.9200444146293232 * kFScale),
+	(uint64)(0.9834714538216174 * kFScale), (uint64)(0.9944598480048967 * kFScale)};
+
+
+static void
+_LoadavgUpdate(void *data, int iteration)
+{
+	uint64 threadCount = 0;
+	for (int i = 0; i < gCoreCount; i++)
+		threadCount += gCoreEntries[i].ThreadCount();
+	threadCount--;
+	for (int i = 0; i < 3; i++) {
+		sAverageRunnable.ldavg[i]
+			= (sCExp[i] * sAverageRunnable.ldavg[i] + threadCount * kFScale * (kFScale - sCExp[i]))
+			>> kFShift;
+	}
+}
+
+
+status_t
+scheduler_loadavg_init()
+{
+	register_kernel_daemon(_LoadavgUpdate, NULL, 50);
+		// run the daemon once five second
+
+	return B_OK;
+}
+
+
+// #pragma mark - Syscalls
+
+
+status_t
+_user_get_loadavg(struct loadavg* userInfo, size_t size)
+{
+	if (userInfo == NULL || !IS_USER_ADDRESS(userInfo))
+		return B_BAD_ADDRESS;
+	if (size != sizeof(struct loadavg))
+		return B_BAD_VALUE;
+	if (user_memcpy(userInfo, &sAverageRunnable, sizeof(struct loadavg)) < B_OK)
+		return B_BAD_ADDRESS;
+
+	return B_OK;
+}

src/tests/libs/bsd/Jamfile

@@ -3,6 +3,7 @@ SubDir HAIKU_TOP src tests libs bsd ;
 UseHeaders [ FDirName $(HAIKU_TOP) headers compatibility bsd ] : true ;
 
 SimpleTest forkpty_test : forkpty.c : libbsd.so ;
+SimpleTest getloadavg_test : getloadavg_test.cpp : libbsd.so ;
 SimpleTest wait4_test : wait4_test.cpp : libbsd.so ;
 
 

src/tests/libs/bsd/getloadavg_test.cpp

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2025, Jérôme Duval, jerome.duval@gmail.com. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ */
+
+
+#include <cinttypes>
+#include <stdio.h>
+#include <stdlib.h>
+
+
+int
+main(int argc, char** argv)
+{
+	double loadavg[3];
+	int count = getloadavg(loadavg, 3);
+	if (count == -1)
+		return 1;
+	printf("getloadavg() returned %" PRId32 ", values %f %f %f\n", count, loadavg[0], loadavg[1],
+		loadavg[2]);
+
+	return 0;
+}