diff options
author | Dave Marchevsky <davemarchevsky@fb.com> | 2022-07-05 12:00:18 -0700 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-07-07 16:35:21 +0200 |
commit | 2b4b2621fd6401865b31b9f403e4b936b7439e94 (patch) | |
tree | fa77994c04a9e5317a655a39f7f11cfbf64ee493 /tools/testing/selftests/bpf/benchs | |
parent | 935dc35c75318fa213d26808ad8bb130fb0b486e (diff) |
selftests/bpf: Add benchmark for local_storage RCU Tasks Trace usage
This benchmark measures grace period latency and kthread cpu usage of
RCU Tasks Trace when many processes are creating/deleting BPF
local_storage. Intent here is to quantify improvement on these metrics
after Paul's recent RCU Tasks patches [0].
Specifically, fork 15k tasks which call a bpf prog that creates/destroys
task local_storage and sleep in a loop, resulting in many
call_rcu_tasks_trace calls.
To determine grace period latency, trace time elapsed between
rcu_tasks_trace_pregp_step and rcu_tasks_trace_postgp; for cpu usage
look at rcu_task_trace_kthread's stime in /proc/PID/stat.
On my virtualized test environment (Skylake, 8 cpus) benchmark results
demonstrate significant improvement:
BEFORE Paul's patches:
SUMMARY tasks_trace grace period latency avg 22298.551 us stddev 1302.165 us
SUMMARY ticks per tasks_trace grace period avg 2.291 stddev 0.324
AFTER Paul's patches:
SUMMARY tasks_trace grace period latency avg 16969.197 us stddev 2525.053 us
SUMMARY ticks per tasks_trace grace period avg 1.146 stddev 0.178
Note that since these patches are not in bpf-next benchmarking was done
by cherry-picking this patch onto rcu tree.
[0] https://lore.kernel.org/rcu/20220620225402.GA3842369@paulmck-ThinkPad-P17-Gen-1/
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220705190018.3239050-1-davemarchevsky@fb.com
Diffstat (limited to 'tools/testing/selftests/bpf/benchs')
-rw-r--r-- | tools/testing/selftests/bpf/benchs/bench_local_storage_rcu_tasks_trace.c | 281 | ||||
-rwxr-xr-x | tools/testing/selftests/bpf/benchs/run_bench_local_storage_rcu_tasks_trace.sh | 11 |
2 files changed, 292 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/benchs/bench_local_storage_rcu_tasks_trace.c b/tools/testing/selftests/bpf/benchs/bench_local_storage_rcu_tasks_trace.c new file mode 100644 index 000000000000..43f109d93130 --- /dev/null +++ b/tools/testing/selftests/bpf/benchs/bench_local_storage_rcu_tasks_trace.c @@ -0,0 +1,281 @@ +// 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) { + fprintf(stderr, "couldn't open %s, exiting\n", procfs_path); + goto err_out; + } + if (fscanf(f, "%*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %ld", &stime) != 1) { + fprintf(stderr, "fscanf of %s failed, exiting\n", procfs_path); + goto err_out; + } + fclose(f); + return stime; + +err_out: + if (f) + fclose(f); + exit(1); + return 0; +} + +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", errno); + goto err_out; + } + + if (getppid() != runner_pid) { + fprintf(stderr, "Runner died while spinning up procs, exiting\n"); + goto err_out; + } + sleep_and_loop(); + } + } + printf("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, +}; diff --git a/tools/testing/selftests/bpf/benchs/run_bench_local_storage_rcu_tasks_trace.sh b/tools/testing/selftests/bpf/benchs/run_bench_local_storage_rcu_tasks_trace.sh new file mode 100755 index 000000000000..5dac1f02892c --- /dev/null +++ b/tools/testing/selftests/bpf/benchs/run_bench_local_storage_rcu_tasks_trace.sh @@ -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 |