I did some benchmarking on an intel box (Intel(R) Xeon(R) D-2191A CPU @ 1.60GHz)
which has 20 cores and 80 cpus. The number of hits are in the unit
of loop iterations.
The following are two benchmark results and a few other tries show
similar results in terms of variation.
$ ./benchs/run_bench_private_stack.sh
no-private-stack-1: 2.152 ± 0.004M/s (drops 0.000 ± 0.000M/s)
private-stack-1: 2.226 ± 0.003M/s (drops 0.000 ± 0.000M/s)
no-private-stack-8: 89.086 ± 0.674M/s (drops 0.000 ± 0.000M/s)
private-stack-8: 90.023 ± 0.117M/s (drops 0.000 ± 0.000M/s)
no-private-stack-64: 1545.383 ± 3.574M/s (drops 0.000 ± 0.000M/s)
private-stack-64: 1534.630 ± 2.063M/s (drops 0.000 ± 0.000M/s)
no-private-stack-512: 14591.591 ± 15.202M/s (drops 0.000 ± 0.000M/s)
private-stack-512: 14323.796 ± 13.165M/s (drops 0.000 ± 0.000M/s)
no-private-stack-2048: 58680.977 ± 46.116M/s (drops 0.000 ± 0.000M/s)
private-stack-2048: 58614.699 ± 22.031M/s (drops 0.000 ± 0.000M/s)
no-private-stack-4096: 119974.497 ± 90.985M/s (drops 0.000 ± 0.000M/s)
private-stack-4096: 114841.949 ± 59.514M/s (drops 0.000 ± 0.000M/s)
$ ./benchs/run_bench_private_stack.sh
no-private-stack-1: 2.246 ± 0.002M/s (drops 0.000 ± 0.000M/s)
private-stack-1: 2.232 ± 0.005M/s (drops 0.000 ± 0.000M/s)
no-private-stack-8: 91.446 ± 0.055M/s (drops 0.000 ± 0.000M/s)
private-stack-8: 90.120 ± 0.069M/s (drops 0.000 ± 0.000M/s)
no-private-stack-64: 1578.374 ± 1.508M/s (drops 0.000 ± 0.000M/s)
private-stack-64: 1514.909 ± 3.898M/s (drops 0.000 ± 0.000M/s)
no-private-stack-512: 14767.811 ± 22.399M/s (drops 0.000 ± 0.000M/s)
private-stack-512: 14232.382 ± 227.217M/s (drops 0.000 ± 0.000M/s)
no-private-stack-2048: 58342.372 ± 81.519M/s (drops 0.000 ± 0.000M/s)
private-stack-2048: 54503.335 ± 160.199M/s (drops 0.000 ± 0.000M/s)
no-private-stack-4096: 117262.975 ± 179.802M/s (drops 0.000 ± 0.000M/s)
private-stack-4096: 114643.523 ± 146.956M/s (drops 0.000 ± 0.000M/s)
It is is clear that private-stack is worse than non-private stack up to close 5 percents.
This can be roughly estimated based on the above jit code with no-private-stack vs. private-stack.
Although the benchmark shows up to 5% potential slowdown with private stack.
In reality, the kernel enables private stack only after stack size 64 which means
the bpf prog will do some useful things. If bpf prog uses any helper/kfunc, the
push/pop r9 overhead should be minimum compared to the overhead of helper/kfunc.
if the prog does not use a lot of helper/kfunc, there is no push/pop r9 and
the performance should be reasonable too.
With 4096 loop ierations per program run, I got
$ perf record -- ./bench -w3 -d10 -a --nr-batch-iters=4096 no-private-stack
18.47% bench [k]
17.29% bench bpf_trampoline_6442522961 [k] bpf_trampoline_6442522961
13.33% bench bpf_prog_bcf7977d3b93787c_func1 [k] bpf_prog_bcf7977d3b93787c_func1
11.86% bench [kernel.vmlinux] [k] migrate_enable
11.60% bench [kernel.vmlinux] [k] __bpf_prog_enter_recur
11.42% bench [kernel.vmlinux] [k] __bpf_prog_exit_recur
7.87% bench [kernel.vmlinux] [k] migrate_disable
3.71% bench [kernel.vmlinux] [k] bpf_get_numa_node_id
3.67% bench bpf_prog_d9703036495d54b0_trigger_driver [k] bpf_prog_d9703036495d54b0_trigger_driver
0.04% bench bench [.] btf_validate_type
$ perf record -- ./bench -w3 -d10 -a --nr-batch-iters=4096 private-stack
18.94% bench [k]
16.88% bench bpf_prog_bcf7977d3b93787c_func1 [k] bpf_prog_bcf7977d3b93787c_func1
15.77% bench bpf_trampoline_6442522961 [k] bpf_trampoline_6442522961
11.70% bench [kernel.vmlinux] [k] __bpf_prog_enter_recur
11.48% bench [kernel.vmlinux] [k] migrate_enable
11.30% bench [kernel.vmlinux] [k] __bpf_prog_exit_recur
5.85% bench [kernel.vmlinux] [k] migrate_disable
3.69% bench bpf_prog_d9703036495d54b0_trigger_driver [k] bpf_prog_d9703036495d54b0_trigger_driver
3.56% bench [kernel.vmlinux] [k] bpf_get_numa_node_id
0.06% bench bench [.] bpf_prog_test_run_opts
NOTE: I tried 6.4 perf and 6.10 perf, both of which have issues. I will investigate this further.
I suspect top 18.47%/18.94% perf run probably due to fentry prog bench_trigger_fentry_batch,
considering even subprog func1 takes 13.33%/16.88% time.
Overall bpf prog include trampoline takes more than 50% of the time.
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
arch/x86/net/bpf_jit_comp.c | 5 +-
include/linux/bpf.h | 3 +-
include/uapi/linux/bpf.h | 3 +
kernel/bpf/core.c | 3 +-
kernel/bpf/syscall.c | 4 +-
kernel/bpf/verifier.c | 1 +
tools/include/uapi/linux/bpf.h | 3 +
tools/testing/selftests/bpf/Makefile | 2 +
tools/testing/selftests/bpf/bench.c | 6 +
.../bpf/benchs/bench_private_stack.c | 149 ++++++++++++++++++
.../bpf/benchs/run_bench_private_stack.sh | 11 ++
.../selftests/bpf/progs/private_stack.c | 37 +++++
12 files changed, 222 insertions(+), 5 deletions(-)
create mode 100644 tools/testing/selftests/bpf/benchs/bench_private_stack.c
create mode 100755 tools/testing/selftests/bpf/benchs/run_bench_private_stack.sh
create mode 100644 tools/testing/selftests/bpf/progs/private_stack.c
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 60f5d86fb6aa..3f12f7a957ba 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -3327,7 +3327,10 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
skip_init_addrs:
if (bpf_enable_private_stack(prog) && !prog->private_stack_ptr) {
- private_stack_ptr = __alloc_percpu_gfp(prog->aux->stack_depth, 8, GFP_KERNEL);
+ if (prog->aux->stack_depth == 0)
+ private_stack_ptr = __alloc_percpu_gfp(8, 8, GFP_KERNEL);
+ else
+ private_stack_ptr = __alloc_percpu_gfp(prog->aux->stack_depth, 8, GFP_KERNEL);
if (!private_stack_ptr) {
prog = orig_prog;
goto out_addrs;
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 19a3f5355363..2f8708465c19 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1551,7 +1551,8 @@ struct bpf_prog {
call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */
call_get_func_ip:1, /* Do we call get_func_ip() */
tstamp_type_access:1, /* Accessed __sk_buff->tstamp_type */
- sleepable:1; /* BPF program is sleepable */
+ sleepable:1, /* BPF program is sleepable */
+ disable_private_stack:1; /* Disable private stack */
enum bpf_prog_type type; /* Type of BPF program */
enum bpf_attach_type expected_attach_type; /* For some prog types */
u32 len; /* Number of filter blocks */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 35bcf52dbc65..98af8ea8a4d6 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1409,6 +1409,9 @@ enum {
/* Do not translate kernel bpf_arena pointers to user pointers */
BPF_F_NO_USER_CONV = (1U << 18),
+
+/* Disable private stack */
+ BPF_F_DISABLE_PRIVATE_STACK = (1U << 19),
};
/* Flags for BPF_PROG_QUERY. */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index f69eb0c5fe03..b5d33cf87695 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2815,14 +2815,13 @@ EXPORT_SYMBOL_GPL(bpf_prog_free);
bool bpf_enable_private_stack(struct bpf_prog *prog)
{
- if (prog->aux->stack_depth <= 64)
+ if (prog->disable_private_stack)
return false;
switch (prog->aux->prog->type) {
case BPF_PROG_TYPE_KPROBE:
case BPF_PROG_TYPE_TRACEPOINT:
case BPF_PROG_TYPE_PERF_EVENT:
- case BPF_PROG_TYPE_RAW_TRACEPOINT:
return true;
case BPF_PROG_TYPE_TRACING:
if (prog->expected_attach_type != BPF_TRACE_ITER)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 89162ddb4747..bb2b632c9c2c 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2715,7 +2715,8 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
BPF_F_XDP_HAS_FRAGS |
BPF_F_XDP_DEV_BOUND_ONLY |
BPF_F_TEST_REG_INVARIANTS |
- BPF_F_TOKEN_FD))
+ BPF_F_TOKEN_FD |
+ BPF_F_DISABLE_PRIVATE_STACK))
return -EINVAL;
bpf_prog_load_fixup_attach_type(attr);
@@ -2828,6 +2829,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
prog->expected_attach_type = attr->expected_attach_type;
prog->sleepable = !!(attr->prog_flags & BPF_F_SLEEPABLE);
+ prog->disable_private_stack = !!(attr->prog_flags & BPF_F_DISABLE_PRIVATE_STACK);
prog->aux->attach_btf = attach_btf;
prog->aux->attach_btf_id = attr->attach_btf_id;
prog->aux->dst_prog = dst_prog;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8da132a1ef28..397b2b9eed24 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19442,6 +19442,7 @@ static int jit_subprogs(struct bpf_verifier_env *env)
goto out_free;
func[i]->is_func = 1;
func[i]->sleepable = prog->sleepable;
+ func[i]->disable_private_stack = prog->disable_private_stack;
func[i]->aux->func_idx = i;
/* Below members will be freed only at prog->aux */
func[i]->aux->btf = prog->aux->btf;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 35bcf52dbc65..98af8ea8a4d6 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1409,6 +1409,9 @@ enum {
/* Do not translate kernel bpf_arena pointers to user pointers */
BPF_F_NO_USER_CONV = (1U << 18),
+
+/* Disable private stack */
+ BPF_F_DISABLE_PRIVATE_STACK = (1U << 19),
};
/* Flags for BPF_PROG_QUERY. */
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index dd49c1d23a60..44a6a43da71c 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -733,6 +733,7 @@ $(OUTPUT)/bench_local_storage_create.o: $(OUTPUT)/bench_local_storage_create.ske
$(OUTPUT)/bench_bpf_hashmap_lookup.o: $(OUTPUT)/bpf_hashmap_lookup.skel.h
$(OUTPUT)/bench_htab_mem.o: $(OUTPUT)/htab_mem_bench.skel.h
$(OUTPUT)/bench_bpf_crypto.o: $(OUTPUT)/crypto_bench.skel.h
+$(OUTPUT)/bench_private_stack.o: $(OUTPUT)/private_stack.skel.h
$(OUTPUT)/bench.o: bench.h testing_helpers.h $(BPFOBJ)
$(OUTPUT)/bench: LDLIBS += -lm
$(OUTPUT)/bench: $(OUTPUT)/bench.o \
@@ -753,6 +754,7 @@ $(OUTPUT)/bench: $(OUTPUT)/bench.o \
$(OUTPUT)/bench_local_storage_create.o \
$(OUTPUT)/bench_htab_mem.o \
$(OUTPUT)/bench_bpf_crypto.o \
+ $(OUTPUT)/bench_private_stack.o \
#
$(call msg,BINARY,,$@)
$(Q)$(CC) $(CFLAGS) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@
diff --git a/tools/testing/selftests/bpf/bench.c b/tools/testing/selftests/bpf/bench.c
index 627b74ae041b..4f4867cd80f9 100644
--- a/tools/testing/selftests/bpf/bench.c
+++ b/tools/testing/selftests/bpf/bench.c
@@ -282,6 +282,7 @@ extern struct argp bench_local_storage_create_argp;
extern struct argp bench_htab_mem_argp;
extern struct argp bench_trigger_batch_argp;
extern struct argp bench_crypto_argp;
+extern struct argp bench_private_stack_argp;
static const struct argp_child bench_parsers[] = {
{ &bench_ringbufs_argp, 0, "Ring buffers benchmark", 0 },
@@ -296,6 +297,7 @@ static const struct argp_child bench_parsers[] = {
{ &bench_htab_mem_argp, 0, "hash map memory benchmark", 0 },
{ &bench_trigger_batch_argp, 0, "BPF triggering benchmark", 0 },
{ &bench_crypto_argp, 0, "bpf crypto benchmark", 0 },
+ { &bench_private_stack_argp, 0, "bpf private stack benchmark", 0 },
{},
};
@@ -542,6 +544,8 @@ extern const struct bench bench_local_storage_create;
extern const struct bench bench_htab_mem;
extern const struct bench bench_crypto_encrypt;
extern const struct bench bench_crypto_decrypt;
+extern const struct bench bench_no_private_stack;
+extern const struct bench bench_private_stack;
static const struct bench *benchs[] = {
&bench_count_global,
@@ -596,6 +600,8 @@ static const struct bench *benchs[] = {
&bench_htab_mem,
&bench_crypto_encrypt,
&bench_crypto_decrypt,
+ &bench_no_private_stack,
+ &bench_private_stack,
};
static void find_benchmark(void)
diff --git a/tools/testing/selftests/bpf/benchs/bench_private_stack.c b/tools/testing/selftests/bpf/benchs/bench_private_stack.c
new file mode 100644
index 000000000000..5ae1e9bfe706
--- /dev/null
+++ b/tools/testing/selftests/bpf/benchs/bench_private_stack.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+
+#include <argp.h>
+#include "bench.h"
+#include "private_stack.skel.h"
+
+static struct ctx {
+ struct private_stack *skel;
+} ctx;
+
+static struct {
+ long nr_batch_iters;
+} args = {
+ .nr_batch_iters = 0,
+};
+
+enum {
+ ARG_NR_BATCH_ITERS = 3000,
+};
+
+static const struct argp_option opts[] = {
+ { "nr-batch-iters", ARG_NR_BATCH_ITERS, "NR_BATCH_ITERS",
+ 0, "nr batch iters" },
+ {},
+};
+
+static error_t private_stack_parse_arg(int key, char *arg, struct argp_state *state)
+{
+ long ret;
+
+ switch (key) {
+ case ARG_NR_BATCH_ITERS:
+ ret = strtoul(arg, NULL, 10);
+ if (ret < 1)
+ argp_usage(state);
+ args.nr_batch_iters = ret;
+ break;
+ default:
+ return ARGP_ERR_UNKNOWN;
+ }
+
+ return 0;
+}
+
+const struct argp bench_private_stack_argp = {
+ .options = opts,
+ .parser = private_stack_parse_arg,
+};
+
+static void private_stack_validate(void)
+{
+ if (env.consumer_cnt != 0) {
+ fprintf(stderr,
+ "The private stack benchmarks do not support consumer\n");
+ exit(1);
+ }
+}
+
+static void common_setup(bool disable_private_stack)
+{
+ struct private_stack *skel;
+ struct bpf_link *link;
+ __u32 old_flags;
+ int err;
+
+ skel = private_stack__open();
+ if(!skel) {
+ fprintf(stderr, "failed to open skeleton\n");
+ exit(1);
+ }
+ ctx.skel = skel;
+
+ if (disable_private_stack) {
+ old_flags = bpf_program__flags(skel->progs.bench_trigger_fentry_batch);
+ bpf_program__set_flags(skel->progs.bench_trigger_fentry_batch, old_flags | BPF_F_DISABLE_PRIVATE_STACK);
+ }
+
+ skel->rodata->batch_iters = args.nr_batch_iters;
+
+ err = private_stack__load(skel);
+ if (err) {
+ fprintf(stderr, "failed to load program\n");
+ exit(1);
+ }
+
+ link = bpf_program__attach(skel->progs.bench_trigger_fentry_batch);
+ if (!link) {
+ fprintf(stderr, "failed to attach program bench_trigger_fentry_batch\n");
+ exit(1);
+ }
+}
+
+static void no_private_stack_setup(void)
+{
+ common_setup(true);
+}
+
+static void private_stack_setup(void)
+{
+ common_setup(false);
+}
+
+static void private_stack_measure(struct bench_res *res)
+{
+ struct private_stack *skel = ctx.skel;
+ unsigned long total_hits = 0;
+ static unsigned long last_hits;
+
+ total_hits = skel->bss->hits * skel->rodata->batch_iters;
+ res->hits = total_hits - last_hits;
+ res->drops = 0;
+ res->false_hits = 0;
+ last_hits = total_hits;
+}
+
+static void *private_stack_producer(void *unused)
+{
+ struct private_stack *skel = ctx.skel;
+ int fd;
+
+ fd = bpf_program__fd(skel->progs.trigger_driver);
+ while (true)
+ bpf_prog_test_run_opts(fd, NULL);
+
+ return NULL;
+}
+
+const struct bench bench_no_private_stack = {
+ .name = "no-private-stack",
+ .argp = &bench_private_stack_argp,
+ .validate = private_stack_validate,
+ .setup = no_private_stack_setup,
+ .producer_thread = private_stack_producer,
+ .measure = private_stack_measure,
+ .report_progress = hits_drops_report_progress,
+ .report_final = hits_drops_report_final,
+};
+
+const struct bench bench_private_stack = {
+ .name = "private-stack",
+ .argp = &bench_private_stack_argp,
+ .validate = private_stack_validate,
+ .setup = private_stack_setup,
+ .producer_thread = private_stack_producer,
+ .measure = private_stack_measure,
+ .report_progress = hits_drops_report_progress,
+ .report_final = hits_drops_report_final,
+};
diff --git a/tools/testing/selftests/bpf/benchs/run_bench_private_stack.sh b/tools/testing/selftests/bpf/benchs/run_bench_private_stack.sh
new file mode 100755
index 000000000000..692a5f9676a7
--- /dev/null
+++ b/tools/testing/selftests/bpf/benchs/run_bench_private_stack.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+source ./benchs/run_common.sh
+
+set -eufo pipefail
+
+for b in 1 8 64 512 2048 4096; do
+ summarize "no-private-stack-${b}: " "$($RUN_BENCH --nr-batch-iters=${b} no-private-stack)"
+ summarize "private-stack-${b}: " "$($RUN_BENCH --nr-batch-iters=${b} private-stack)"
+done
diff --git a/tools/testing/selftests/bpf/progs/private_stack.c b/tools/testing/selftests/bpf/progs/private_stack.c
new file mode 100644
index 000000000000..81d2efad5890
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/private_stack.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+#include <linux/types.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+unsigned long hits = 0;
+const volatile int batch_iters = 0;
+
+SEC("raw_tp")
+int trigger_driver(void *ctx)
+{
+ int i;
+
+ for (i = 0; i < batch_iters; i++)
+ (void)bpf_get_numa_node_id(); /* attach point for benchmarking */
+
+ return 0;
+}
+
+__attribute__((weak)) int func1(void) {
+ return 0;
+}
+
+SEC("fentry/bpf_get_numa_node_id")
+int bench_trigger_fentry_batch(void *ctx)
+{
+ hits++;
+ (void)func1();
+ (void)func1();
+ (void)func1();
+ return 0;
+}
+
--
2.43.0
