On Thu, Jun 23, 2022 at 04:46:09PM -0700, Dave Marchevsky wrote:
> +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);
> +}
> +
[ ... ]
> 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
> diff --git a/tools/testing/selftests/bpf/progs/local_storage_rcu_tasks_trace_bench.c b/tools/testing/selftests/bpf/progs/local_storage_rcu_tasks_trace_bench.c
> new file mode 100644
> index 000000000000..9b11342b19a0
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/local_storage_rcu_tasks_trace_bench.c
> @@ -0,0 +1,65 @@
> +// 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;
> +
> +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("kprobe/rcu_tasks_trace_pregp_step")
nit. Similar to the fentry sys_getpgid above.
may as well use fentry for everything.
> +int pregp_step(struct pt_regs *ctx)
> +{
> + current_gp_start = bpf_ktime_get_ns();
> + return 0;
> +}
> +
> +SEC("kprobe/rcu_tasks_trace_postgp")
> +int postgp(struct pt_regs *ctx)
> +{
> + if (!current_gp_start) {
> + /* Will only happen if prog tracing rcu_tasks_trace_pregp_step doesn't
> + * execute before this prog
> + */
> + __sync_add_and_fetch(&unexpected, 1);
I consistently hit this:
./bench --nr_procs 1500 --kthread_pid ... -d 60 --quiet 1 local-storage-tasks-trace
Setting up benchmark 'local-storage-tasks-trace'...
Spun up 1500 procs (our pid 28351)
Benchmark 'local-storage-tasks-trace' started.
Error: Unexpected order of bpf prog calls (postgp after pregp).Data can't be trusted, exiting
May be there is a chance for the very first postgp being called
before the pregp_step?
Thanks for working on this!
