xxx

scheds/c/meson.build

@@ -1,5 +1,5 @@
 c_scheds = ['scx_simple', 'scx_qmap', 'scx_central', 'scx_userland', 'scx_nest',
-            'scx_flatcg', 'scx_pair']
+            'scx_flatcg', 'scx_pair', 'scx_sdt']
 
 foreach sched: c_scheds
   thread_dep = dependency('threads')

scheds/c/scx_sdt.bpf.c

@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <scx/common.bpf.h>
+
+char _license[] SEC("license") = "GPL";
+
+UEI_DEFINE(uei);
+
+#define SHARED_DSQ 0
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(key_size, sizeof(u32));
+	__uint(value_size, sizeof(u64));
+	__uint(max_entries, 2);			/* [local, global] */
+} stats SEC(".maps");
+
+static void stat_inc(u32 idx)
+{
+	u64 *cnt_p = bpf_map_lookup_elem(&stats, &idx);
+	if (cnt_p)
+		(*cnt_p)++;
+}
+
+s32 BPF_STRUCT_OPS(sdt_select_cpu, struct task_struct *p, s32 prev_cpu, u64 wake_flags)
+{
+	bool is_idle = false;
+	s32 cpu;
+
+	cpu = scx_bpf_select_cpu_dfl(p, prev_cpu, wake_flags, &is_idle);
+	if (is_idle) {
+		stat_inc(0);	/* count local queueing */
+		scx_bpf_dispatch(p, SCX_DSQ_LOCAL, SCX_SLICE_DFL, 0);
+	}
+
+	return cpu;
+}
+
+void BPF_STRUCT_OPS(sdt_enqueue, struct task_struct *p, u64 enq_flags)
+{
+	stat_inc(1);	/* count global queueing */
+
+	scx_bpf_dispatch(p, SHARED_DSQ, SCX_SLICE_DFL, enq_flags);
+}
+
+void BPF_STRUCT_OPS(sdt_dispatch, s32 cpu, struct task_struct *prev)
+{
+	scx_bpf_consume(SHARED_DSQ);
+}
+
+s32 BPF_STRUCT_OPS_SLEEPABLE(sdt_init)
+{
+	return scx_bpf_create_dsq(SHARED_DSQ, -1);
+}
+
+void BPF_STRUCT_OPS(sdt_exit, struct scx_exit_info *ei)
+{
+	UEI_RECORD(uei, ei);
+}
+
+SCX_OPS_DEFINE(sdt_ops,
+	       .select_cpu		= (void *)sdt_select_cpu,
+	       .enqueue			= (void *)sdt_enqueue,
+	       .dispatch		= (void *)sdt_dispatch,
+	       .init			= (void *)sdt_init,
+	       .exit			= (void *)sdt_exit,
+	       .name			= "sdt");

scheds/c/scx_sdt.c

@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
+ * Copyright (c) 2022 Tejun Heo <tj@kernel.org>
+ * Copyright (c) 2022 David Vernet <dvernet@meta.com>
+ */
+#include <stdio.h>
+#include <unistd.h>
+#include <signal.h>
+#include <libgen.h>
+#include <bpf/bpf.h>
+#include <scx/common.h>
+#include "scx_sdt.bpf.skel.h"
+
+const char help_fmt[] =
+"A simple sched_ext scheduler.\n"
+"\n"
+"See the top-level comment in .bpf.c for more details.\n"
+"\n"
+"Usage: %s [-f] [-v]\n"
+"\n"
+"  -v            Print libbpf debug messages\n"
+"  -h            Display this help and exit\n";
+
+static bool verbose;
+static volatile int exit_req;
+
+static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
+{
+	if (level == LIBBPF_DEBUG && !verbose)
+		return 0;
+	return vfprintf(stderr, format, args);
+}
+
+static void sigint_handler(int sig)
+{
+	exit_req = 1;
+}
+
+static void read_stats(struct scx_sdt *skel, __u64 *stats)
+{
+	int nr_cpus = libbpf_num_possible_cpus();
+	__u64 cnts[2][nr_cpus];
+	__u32 idx;
+
+	memset(stats, 0, sizeof(stats[0]) * 2);
+
+	for (idx = 0; idx < 2; idx++) {
+		int ret, cpu;
+
+		ret = bpf_map_lookup_elem(bpf_map__fd(skel->maps.stats),
+					  &idx, cnts[idx]);
+		if (ret < 0)
+			continue;
+		for (cpu = 0; cpu < nr_cpus; cpu++)
+			stats[idx] += cnts[idx][cpu];
+	}
+}
+
+int main(int argc, char **argv)
+{
+	struct scx_sdt *skel;
+	struct bpf_link *link;
+	__u32 opt;
+	__u64 ecode;
+
+	libbpf_set_print(libbpf_print_fn);
+	signal(SIGINT, sigint_handler);
+	signal(SIGTERM, sigint_handler);
+restart:
+	skel = SCX_OPS_OPEN(sdt_ops, scx_sdt);
+
+	while ((opt = getopt(argc, argv, "fvh")) != -1) {
+		switch (opt) {
+		case 'v':
+			verbose = true;
+			break;
+		default:
+			fprintf(stderr, help_fmt, basename(argv[0]));
+			return opt != 'h';
+		}
+	}
+
+	SCX_OPS_LOAD(skel, sdt_ops, scx_sdt, uei);
+	link = SCX_OPS_ATTACH(skel, sdt_ops, scx_sdt);
+
+	while (!exit_req && !UEI_EXITED(skel, uei)) {
+		__u64 stats[2];
+
+		read_stats(skel, stats);
+		printf("local=%llu global=%llu\n", stats[0], stats[1]);
+		fflush(stdout);
+		sleep(1);
+	}
+
+	bpf_link__destroy(link);
+	ecode = UEI_REPORT(skel, uei);
+	scx_sdt__destroy(skel);
+
+	if (UEI_ECODE_RESTART(ecode))
+		goto restart;
+	return 0;
+}