@@ -572,6 +572,7 @@ $(OUTPUT)/bench_bpf_loop.o: $(OUTPUT)/bpf_loop_bench.skel.h
$(OUTPUT)/bench_strncmp.o: $(OUTPUT)/strncmp_bench.skel.h
$(OUTPUT)/bench_bpf_hashmap_full_update.o: $(OUTPUT)/bpf_hashmap_full_update_bench.skel.h
$(OUTPUT)/bench_local_storage.o: $(OUTPUT)/local_storage_bench.skel.h
+$(OUTPUT)/bench_local_storage_rcu_tasks_trace.o: $(OUTPUT)/local_storage_rcu_tasks_trace_bench.skel.h
$(OUTPUT)/bench.o: bench.h testing_helpers.h $(BPFOBJ)
$(OUTPUT)/bench: LDLIBS += -lm
$(OUTPUT)/bench: $(OUTPUT)/bench.o \
@@ -585,7 +586,8 @@ $(OUTPUT)/bench: $(OUTPUT)/bench.o \
$(OUTPUT)/bench_bpf_loop.o \
$(OUTPUT)/bench_strncmp.o \
$(OUTPUT)/bench_bpf_hashmap_full_update.o \
- $(OUTPUT)/bench_local_storage.o
+ $(OUTPUT)/bench_local_storage.o \
+ $(OUTPUT)/bench_local_storage_rcu_tasks_trace.o
$(call msg,BINARY,,$@)
$(Q)$(CC) $(CFLAGS) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@
@@ -79,6 +79,43 @@ void hits_drops_report_progress(int iter, struct bench_res *res, long delta_ns)
hits_per_sec, hits_per_prod, drops_per_sec, hits_per_sec + drops_per_sec);
}
+void
+grace_period_latency_basic_stats(struct bench_res res[], int res_cnt, struct basic_stats *gp_stat)
+{
+ int i;
+
+ memset(gp_stat, 0, sizeof(struct basic_stats));
+
+ for (i = 0; i < res_cnt; i++)
+ gp_stat->mean += res[i].gp_ns / 1000.0 / (double)res[i].gp_ct / (0.0 + res_cnt);
+
+#define IT_MEAN_DIFF (res[i].gp_ns / 1000.0 / (double)res[i].gp_ct - gp_stat->mean)
+ if (res_cnt > 1) {
+ for (i = 0; i < res_cnt; i++)
+ gp_stat->stddev += (IT_MEAN_DIFF * IT_MEAN_DIFF) / (res_cnt - 1.0);
+ }
+ gp_stat->stddev = sqrt(gp_stat->stddev);
+#undef IT_MEAN_DIFF
+}
+
+void
+grace_period_ticks_basic_stats(struct bench_res res[], int res_cnt, struct basic_stats *gp_stat)
+{
+ int i;
+
+ memset(gp_stat, 0, sizeof(struct basic_stats));
+ for (i = 0; i < res_cnt; i++)
+ gp_stat->mean += res[i].stime / (double)res[i].gp_ct / (0.0 + res_cnt);
+
+#define IT_MEAN_DIFF (res[i].stime / (double)res[i].gp_ct - gp_stat->mean)
+ if (res_cnt > 1) {
+ for (i = 0; i < res_cnt; i++)
+ gp_stat->stddev += (IT_MEAN_DIFF * IT_MEAN_DIFF) / (res_cnt - 1.0);
+ }
+ gp_stat->stddev = sqrt(gp_stat->stddev);
+#undef IT_MEAN_DIFF
+}
+
void hits_drops_report_final(struct bench_res res[], int res_cnt)
{
int i;
@@ -236,6 +273,7 @@ extern struct argp bench_ringbufs_argp;
extern struct argp bench_bloom_map_argp;
extern struct argp bench_bpf_loop_argp;
extern struct argp bench_local_storage_argp;
+extern struct argp bench_local_storage_rcu_tasks_trace_argp;
extern struct argp bench_strncmp_argp;
static const struct argp_child bench_parsers[] = {
@@ -244,6 +282,8 @@ static const struct argp_child bench_parsers[] = {
{ &bench_bpf_loop_argp, 0, "bpf_loop helper benchmark", 0 },
{ &bench_local_storage_argp, 0, "local_storage benchmark", 0 },
{ &bench_strncmp_argp, 0, "bpf_strncmp helper benchmark", 0 },
+ { &bench_local_storage_rcu_tasks_trace_argp, 0,
+ "local_storage RCU Tasks Trace slowdown benchmark", 0 },
{},
};
@@ -449,6 +489,7 @@ extern const struct bench bench_bpf_hashmap_full_update;
extern const struct bench bench_local_storage_cache_seq_get;
extern const struct bench bench_local_storage_cache_interleaved_get;
extern const struct bench bench_local_storage_cache_hashmap_control;
+extern const struct bench bench_local_storage_tasks_trace;
static const struct bench *benchs[] = {
&bench_count_global,
@@ -487,6 +528,7 @@ static const struct bench *benchs[] = {
&bench_local_storage_cache_seq_get,
&bench_local_storage_cache_interleaved_get,
&bench_local_storage_cache_hashmap_control,
+ &bench_local_storage_tasks_trace,
};
static void setup_benchmark()
@@ -30,11 +30,19 @@ struct env {
struct cpu_set cons_cpus;
};
+struct basic_stats {
+ double mean;
+ double stddev;
+};
+
struct bench_res {
long hits;
long drops;
long false_hits;
long important_hits;
+ unsigned long gp_ns;
+ unsigned long gp_ct;
+ unsigned int stime;
};
struct bench {
@@ -65,6 +73,10 @@ void ops_report_final(struct bench_res res[], int res_cnt);
void local_storage_report_progress(int iter, struct bench_res *res,
long delta_ns);
void local_storage_report_final(struct bench_res res[], int res_cnt);
+void grace_period_latency_basic_stats(struct bench_res res[], int res_cnt,
+ struct basic_stats *gp_stat);
+void grace_period_ticks_basic_stats(struct bench_res res[], int res_cnt,
+ struct basic_stats *gp_stat);
static inline __u64 get_time_ns(void)
{
new file mode 100644
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+
+#include <argp.h>
+
+#include <sys/prctl.h>
+#include "local_storage_rcu_tasks_trace_bench.skel.h"
+#include "bench.h"
+
+#include <signal.h>
+
+static struct {
+ __u32 nr_procs;
+ __u32 kthread_pid;
+ bool quiet;
+} args = {
+ .nr_procs = 1000,
+ .kthread_pid = 0,
+ .quiet = false,
+};
+
+enum {
+ ARG_NR_PROCS = 7000,
+ ARG_KTHREAD_PID = 7001,
+ ARG_QUIET = 7002,
+};
+
+static const struct argp_option opts[] = {
+ { "nr_procs", ARG_NR_PROCS, "NR_PROCS", 0,
+ "Set number of user processes to spin up"},
+ { "kthread_pid", ARG_KTHREAD_PID, "PID", 0,
+ "Pid of rcu_tasks_trace kthread for ticks tracking"},
+ { "quiet", ARG_QUIET, "{0,1}", 0,
+ "If true, don't report progress"},
+ {},
+};
+
+static error_t parse_arg(int key, char *arg, struct argp_state *state)
+{
+ long ret;
+
+ switch (key) {
+ case ARG_NR_PROCS:
+ ret = strtol(arg, NULL, 10);
+ if (ret < 1 || ret > UINT_MAX) {
+ fprintf(stderr, "invalid nr_procs\n");
+ argp_usage(state);
+ }
+ args.nr_procs = ret;
+ break;
+ case ARG_KTHREAD_PID:
+ ret = strtol(arg, NULL, 10);
+ if (ret < 1) {
+ fprintf(stderr, "invalid kthread_pid\n");
+ argp_usage(state);
+ }
+ args.kthread_pid = ret;
+ break;
+ case ARG_QUIET:
+ ret = strtol(arg, NULL, 10);
+ if (ret < 0 || ret > 1) {
+ fprintf(stderr, "invalid quiet %ld\n", ret);
+ argp_usage(state);
+ }
+ args.quiet = ret;
+ break;
+break;
+ default:
+ return ARGP_ERR_UNKNOWN;
+ }
+
+ return 0;
+}
+
+const struct argp bench_local_storage_rcu_tasks_trace_argp = {
+ .options = opts,
+ .parser = parse_arg,
+};
+
+#define MAX_SLEEP_PROCS 150000
+
+static void validate(void)
+{
+ if (env.producer_cnt != 1) {
+ fprintf(stderr, "benchmark doesn't support multi-producer!\n");
+ exit(1);
+ }
+ if (env.consumer_cnt != 1) {
+ fprintf(stderr, "benchmark doesn't support multi-consumer!\n");
+ exit(1);
+ }
+
+ if (args.nr_procs > MAX_SLEEP_PROCS) {
+ fprintf(stderr, "benchmark supports up to %u sleeper procs!\n",
+ MAX_SLEEP_PROCS);
+ exit(1);
+ }
+}
+
+static long kthread_pid_ticks(void)
+{
+ char procfs_path[100];
+ long stime;
+ FILE *f;
+
+ if (!args.kthread_pid)
+ return -1;
+
+ sprintf(procfs_path, "/proc/%u/stat", args.kthread_pid);
+ f = fopen(procfs_path, "r");
+ if (f < 0) {
+ fprintf(stderr, "couldn't open %s, exiting\n", procfs_path);
+ exit(1);
+ }
+ fscanf(f, "%*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %ld", &stime);
+ fclose(f);
+ return stime;
+}
+
+static struct {
+ struct local_storage_rcu_tasks_trace_bench *skel;
+ long prev_kthread_stime;
+} ctx;
+
+static void sleep_and_loop(void)
+{
+ while (true) {
+ sleep(rand() % 4);
+ syscall(__NR_getpgid);
+ }
+}
+
+static void local_storage_tasks_trace_setup(void)
+{
+ int i, err, forkret, runner_pid;
+
+ runner_pid = getpid();
+
+ for (i = 0; i < args.nr_procs; i++) {
+ forkret = fork();
+ if (forkret < 0) {
+ fprintf(stderr, "Error forking sleeper proc %u of %u, exiting\n", i,
+ args.nr_procs);
+ goto err_out;
+ }
+
+ if (!forkret) {
+ err = prctl(PR_SET_PDEATHSIG, SIGKILL);
+ if (err < 0) {
+ fprintf(stderr, "prctl failed with err %d, exiting\n", err);
+ goto err_out;
+ }
+
+ if (getppid() != runner_pid) {
+ fprintf(stderr, "Runner died while spinning up procs, exiting\n");
+ goto err_out;
+ }
+ sleep_and_loop();
+ }
+ }
+ fprintf(stderr, "Spun up %u procs (our pid %d)\n", args.nr_procs, runner_pid);
+
+ setup_libbpf();
+
+ ctx.skel = local_storage_rcu_tasks_trace_bench__open_and_load();
+ if (!ctx.skel) {
+ fprintf(stderr, "Error doing open_and_load, exiting\n");
+ goto err_out;
+ }
+
+ ctx.prev_kthread_stime = kthread_pid_ticks();
+
+ if (!bpf_program__attach(ctx.skel->progs.get_local)) {
+ fprintf(stderr, "Error attaching bpf program\n");
+ goto err_out;
+ }
+
+ if (!bpf_program__attach(ctx.skel->progs.pregp_step)) {
+ fprintf(stderr, "Error attaching bpf program\n");
+ goto err_out;
+ }
+
+ if (!bpf_program__attach(ctx.skel->progs.postgp)) {
+ fprintf(stderr, "Error attaching bpf program\n");
+ goto err_out;
+ }
+
+ return;
+err_out:
+ exit(1);
+}
+
+static void measure(struct bench_res *res)
+{
+ long ticks;
+
+ res->gp_ct = atomic_swap(&ctx.skel->bss->gp_hits, 0);
+ res->gp_ns = atomic_swap(&ctx.skel->bss->gp_times, 0);
+ ticks = kthread_pid_ticks();
+ res->stime = ticks - ctx.prev_kthread_stime;
+ ctx.prev_kthread_stime = ticks;
+}
+
+static void *consumer(void *input)
+{
+ return NULL;
+}
+
+static void *producer(void *input)
+{
+ while (true)
+ syscall(__NR_getpgid);
+ return NULL;
+}
+
+static void report_progress(int iter, struct bench_res *res, long delta_ns)
+{
+ if (ctx.skel->bss->unexpected) {
+ fprintf(stderr, "Error: Unexpected order of bpf prog calls (postgp after pregp).");
+ fprintf(stderr, "Data can't be trusted, exiting\n");
+ exit(1);
+ }
+
+ if (args.quiet)
+ return;
+
+ printf("Iter %d\t avg tasks_trace grace period latency\t%lf ns\n",
+ iter, res->gp_ns / (double)res->gp_ct);
+ printf("Iter %d\t avg ticks per tasks_trace grace period\t%lf\n",
+ iter, res->stime / (double)res->gp_ct);
+}
+
+static void report_final(struct bench_res res[], int res_cnt)
+{
+ struct basic_stats gp_stat;
+
+ grace_period_latency_basic_stats(res, res_cnt, &gp_stat);
+ printf("SUMMARY tasks_trace grace period latency");
+ printf("\tavg %.3lf us\tstddev %.3lf us\n", gp_stat.mean, gp_stat.stddev);
+ grace_period_ticks_basic_stats(res, res_cnt, &gp_stat);
+ printf("SUMMARY ticks per tasks_trace grace period");
+ printf("\tavg %.3lf\tstddev %.3lf\n", gp_stat.mean, gp_stat.stddev);
+}
+
+/* local-storage-tasks-trace: Benchmark performance of BPF local_storage's use
+ * of RCU Tasks-Trace.
+ *
+ * Stress RCU Tasks Trace by forking many tasks, all of which do no work aside
+ * from sleep() loop, and creating/destroying BPF task-local storage on wakeup.
+ * The number of forked tasks is configurable.
+ *
+ * exercising code paths which call call_rcu_tasks_trace while there are many
+ * thousands of tasks on the system should result in RCU Tasks-Trace having to
+ * do a noticeable amount of work.
+ *
+ * This should be observable by measuring rcu_tasks_trace_kthread CPU usage
+ * after the grace period has ended, or by measuring grace period latency.
+ *
+ * This benchmark uses both approaches, attaching to rcu_tasks_trace_pregp_step
+ * and rcu_tasks_trace_postgp functions to measure grace period latency and
+ * using /proc/PID/stat to measure rcu_tasks_trace_kthread kernel ticks
+ */
+const struct bench bench_local_storage_tasks_trace = {
+ .name = "local-storage-tasks-trace",
+ .validate = validate,
+ .setup = local_storage_tasks_trace_setup,
+ .producer_thread = producer,
+ .consumer_thread = consumer,
+ .measure = measure,
+ .report_progress = report_progress,
+ .report_final = report_final,
+};
new file mode 100755
@@ -0,0 +1,11 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+kthread_pid=`pgrep rcu_tasks_trace_kthread`
+
+if [ -z $kthread_pid ]; then
+ echo "error: Couldn't find rcu_tasks_trace_kthread"
+ exit 1
+fi
+
+./bench --nr_procs 15000 --kthread_pid $kthread_pid -d 600 --quiet 1 local-storage-tasks-trace
new file mode 100644
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+struct {
+ __uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+ __uint(map_flags, BPF_F_NO_PREALLOC);
+ __type(key, int);
+ __type(value, int);
+} task_storage SEC(".maps");
+
+long hits;
+long gp_hits;
+long gp_times;
+long current_gp_start;
+long unexpected;
+bool postgp_seen;
+
+SEC("fentry/" SYS_PREFIX "sys_getpgid")
+int get_local(void *ctx)
+{
+ struct task_struct *task;
+ int idx;
+ int *s;
+
+ idx = 0;
+ task = bpf_get_current_task_btf();
+ s = bpf_task_storage_get(&task_storage, task, &idx,
+ BPF_LOCAL_STORAGE_GET_F_CREATE);
+ if (!s)
+ return 0;
+
+ *s = 3;
+ bpf_task_storage_delete(&task_storage, task);
+ __sync_add_and_fetch(&hits, 1);
+ return 0;
+}
+
+SEC("fentry/rcu_tasks_trace_pregp_step")
+int pregp_step(struct pt_regs *ctx)
+{
+ current_gp_start = bpf_ktime_get_ns();
+ return 0;
+}
+
+SEC("fentry/rcu_tasks_trace_postgp")
+int postgp(struct pt_regs *ctx)
+{
+ if (!current_gp_start && postgp_seen) {
+ /* Will only happen if prog tracing rcu_tasks_trace_pregp_step doesn't
+ * execute before this prog
+ */
+ __sync_add_and_fetch(&unexpected, 1);
+ return 0;
+ }
+
+ __sync_add_and_fetch(&gp_times, bpf_ktime_get_ns() - current_gp_start);
+ __sync_add_and_fetch(&gp_hits, 1);
+ current_gp_start = 0;
+ postgp_seen = true;
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";