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selftests/bpf: Add benchmark for bpf_strncmp() helper

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Add benchmark to compare the performance between home-made strncmp()
in bpf program and bpf_strncmp() helper. In summary, the performance
win of bpf_strncmp() under x86-64 is greater than 18% when the compared
string length is greater than 64, and is 179% when the length is 4095.
Under arm64 the performance win is even bigger: 33% when the length
is greater than 64 and 600% when the length is 4095.

The following is the details:

no-helper-X: use home-made strncmp() to compare X-sized string
helper-Y: use bpf_strncmp() to compare Y-sized string

Under x86-64:

no-helper-1          3.504 ± 0.000M/s (drops 0.000 ± 0.000M/s)
helper-1             3.347 ± 0.001M/s (drops 0.000 ± 0.000M/s)

no-helper-8          3.357 ± 0.001M/s (drops 0.000 ± 0.000M/s)
helper-8             3.307 ± 0.001M/s (drops 0.000 ± 0.000M/s)

no-helper-32         3.064 ± 0.000M/s (drops 0.000 ± 0.000M/s)
helper-32            3.253 ± 0.001M/s (drops 0.000 ± 0.000M/s)

no-helper-64         2.563 ± 0.001M/s (drops 0.000 ± 0.000M/s)
helper-64            3.040 ± 0.001M/s (drops 0.000 ± 0.000M/s)

no-helper-128        1.975 ± 0.000M/s (drops 0.000 ± 0.000M/s)
helper-128           2.641 ± 0.000M/s (drops 0.000 ± 0.000M/s)

no-helper-512        0.759 ± 0.000M/s (drops 0.000 ± 0.000M/s)
helper-512           1.574 ± 0.000M/s (drops 0.000 ± 0.000M/s)

no-helper-2048       0.329 ± 0.000M/s (drops 0.000 ± 0.000M/s)
helper-2048          0.602 ± 0.000M/s (drops 0.000 ± 0.000M/s)

no-helper-4095       0.117 ± 0.000M/s (drops 0.000 ± 0.000M/s)
helper-4095          0.327 ± 0.000M/s (drops 0.000 ± 0.000M/s)

Under arm64:

no-helper-1          2.806 ± 0.004M/s (drops 0.000 ± 0.000M/s)
helper-1             2.819 ± 0.002M/s (drops 0.000 ± 0.000M/s)

no-helper-8          2.797 ± 0.109M/s (drops 0.000 ± 0.000M/s)
helper-8             2.786 ± 0.025M/s (drops 0.000 ± 0.000M/s)

no-helper-32         2.399 ± 0.011M/s (drops 0.000 ± 0.000M/s)
helper-32            2.703 ± 0.002M/s (drops 0.000 ± 0.000M/s)

no-helper-64         2.020 ± 0.015M/s (drops 0.000 ± 0.000M/s)
helper-64            2.702 ± 0.073M/s (drops 0.000 ± 0.000M/s)

no-helper-128        1.604 ± 0.001M/s (drops 0.000 ± 0.000M/s)
helper-128           2.516 ± 0.002M/s (drops 0.000 ± 0.000M/s)

no-helper-512        0.699 ± 0.000M/s (drops 0.000 ± 0.000M/s)
helper-512           2.106 ± 0.003M/s (drops 0.000 ± 0.000M/s)

no-helper-2048       0.215 ± 0.000M/s (drops 0.000 ± 0.000M/s)
helper-2048          1.223 ± 0.003M/s (drops 0.000 ± 0.000M/s)

no-helper-4095       0.112 ± 0.000M/s (drops 0.000 ± 0.000M/s)
helper-4095          0.796 ± 0.000M/s (drops 0.000 ± 0.000M/s)

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211210141652.877186-4-houtao1@huawei.com
This commit is contained in:
Hou Tao 2021-12-10 22:16:51 +08:00 committed by Alexei Starovoitov
parent 9a93bf3fda
commit 9c42652f8b
5 changed files with 232 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
tools/testing/selftests/bpf/Makefile
View File

@ -537,6 +537,7 @@ $(OUTPUT)/bench_ringbufs.o: $(OUTPUT)/ringbuf_bench.skel.h \
$(OUTPUT)/perfbuf_bench.skel.h
$(OUTPUT)/bench_bloom_filter_map.o: $(OUTPUT)/bloom_filter_bench.skel.h
$(OUTPUT)/bench_bpf_loop.o: $(OUTPUT)/bpf_loop_bench.skel.h
$(OUTPUT)/bench_strncmp.o: $(OUTPUT)/strncmp_bench.skel.h
$(OUTPUT)/bench.o: bench.h testing_helpers.h $(BPFOBJ)
$(OUTPUT)/bench: LDLIBS += -lm
$(OUTPUT)/bench: $(OUTPUT)/bench.o \
@ -547,7 +548,8 @@ $(OUTPUT)/bench: $(OUTPUT)/bench.o \
$(OUTPUT)/bench_trigger.o \
$(OUTPUT)/bench_ringbufs.o \
$(OUTPUT)/bench_bloom_filter_map.o \
$(OUTPUT)/bench_bpf_loop.o
$(OUTPUT)/bench_bpf_loop.o \
$(OUTPUT)/bench_strncmp.o
$(call msg,BINARY,,$@)
$(Q)$(CC) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@

6
tools/testing/selftests/bpf/bench.c
View File

@ -205,11 +205,13 @@ static const struct argp_option opts[] = {
extern struct argp bench_ringbufs_argp;
extern struct argp bench_bloom_map_argp;
extern struct argp bench_bpf_loop_argp;
extern struct argp bench_strncmp_argp;
static const struct argp_child bench_parsers[] = {
{ &bench_ringbufs_argp, 0, "Ring buffers benchmark", 0 },
{ &bench_bloom_map_argp, 0, "Bloom filter map benchmark", 0 },
{ &bench_bpf_loop_argp, 0, "bpf_loop helper benchmark", 0 },
{ &bench_strncmp_argp, 0, "bpf_strncmp helper benchmark", 0 },
{},
};
@ -409,6 +411,8 @@ extern const struct bench bench_bloom_false_positive;
extern const struct bench bench_hashmap_without_bloom;
extern const struct bench bench_hashmap_with_bloom;
extern const struct bench bench_bpf_loop;
extern const struct bench bench_strncmp_no_helper;
extern const struct bench bench_strncmp_helper;
static const struct bench *benchs[] = {
&bench_count_global,
@ -441,6 +445,8 @@ static const struct bench *benchs[] = {
&bench_hashmap_without_bloom,
&bench_hashmap_with_bloom,
&bench_bpf_loop,
&bench_strncmp_no_helper,
&bench_strncmp_helper,
};
static void setup_benchmark()

161
tools/testing/selftests/bpf/benchs/bench_strncmp.c Normal file
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@ -0,0 +1,161 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2021. Huawei Technologies Co., Ltd */
#include <argp.h>
#include "bench.h"
#include "strncmp_bench.skel.h"
static struct strncmp_ctx {
struct strncmp_bench *skel;
} ctx;
static struct strncmp_args {
u32 cmp_str_len;
} args = {
.cmp_str_len = 32,
};
enum {
ARG_CMP_STR_LEN = 5000,
};
static const struct argp_option opts[] = {
{ "cmp-str-len", ARG_CMP_STR_LEN, "CMP_STR_LEN", 0,
"Set the length of compared string" },
{},
};
static error_t strncmp_parse_arg(int key, char *arg, struct argp_state *state)
{
switch (key) {
case ARG_CMP_STR_LEN:
args.cmp_str_len = strtoul(arg, NULL, 10);
if (!args.cmp_str_len ||
args.cmp_str_len >= sizeof(ctx.skel->bss->str)) {
fprintf(stderr, "Invalid cmp str len (limit %zu)\n",
sizeof(ctx.skel->bss->str));
argp_usage(state);
}
break;
default:
return ARGP_ERR_UNKNOWN;
}
return 0;
}
const struct argp bench_strncmp_argp = {
.options = opts,
.parser = strncmp_parse_arg,
};
static void strncmp_validate(void)
{
if (env.consumer_cnt != 1) {
fprintf(stderr, "strncmp benchmark doesn't support multi-consumer!\n");
exit(1);
}
}
static void strncmp_setup(void)
{
int err;
char *target;
size_t i, sz;
sz = sizeof(ctx.skel->rodata->target);
if (!sz || sz < sizeof(ctx.skel->bss->str)) {
fprintf(stderr, "invalid string size (target %zu, src %zu)\n",
sz, sizeof(ctx.skel->bss->str));
exit(1);
}
setup_libbpf();
ctx.skel = strncmp_bench__open();
if (!ctx.skel) {
fprintf(stderr, "failed to open skeleton\n");
exit(1);
}
srandom(time(NULL));
target = ctx.skel->rodata->target;
for (i = 0; i < sz - 1; i++)
target[i] = '1' + random() % 9;
target[sz - 1] = '\0';
ctx.skel->rodata->cmp_str_len = args.cmp_str_len;
memcpy(ctx.skel->bss->str, target, args.cmp_str_len);
ctx.skel->bss->str[args.cmp_str_len] = '\0';
/* Make bss->str < rodata->target */
ctx.skel->bss->str[args.cmp_str_len - 1] -= 1;
err = strncmp_bench__load(ctx.skel);
if (err) {
fprintf(stderr, "failed to load skeleton\n");
strncmp_bench__destroy(ctx.skel);
exit(1);
}
}
static void strncmp_attach_prog(struct bpf_program *prog)
{
struct bpf_link *link;
link = bpf_program__attach(prog);
if (!link) {
fprintf(stderr, "failed to attach program!\n");
exit(1);
}
}
static void strncmp_no_helper_setup(void)
{
strncmp_setup();
strncmp_attach_prog(ctx.skel->progs.strncmp_no_helper);
}
static void strncmp_helper_setup(void)
{
strncmp_setup();
strncmp_attach_prog(ctx.skel->progs.strncmp_helper);
}
static void *strncmp_producer(void *ctx)
{
while (true)
(void)syscall(__NR_getpgid);
return NULL;
}
static void *strncmp_consumer(void *ctx)
{
return NULL;
}
static void strncmp_measure(struct bench_res *res)
{
res->hits = atomic_swap(&ctx.skel->bss->hits, 0);
}
const struct bench bench_strncmp_no_helper = {
.name = "strncmp-no-helper",
.validate = strncmp_validate,
.setup = strncmp_no_helper_setup,
.producer_thread = strncmp_producer,
.consumer_thread = strncmp_consumer,
.measure = strncmp_measure,
.report_progress = hits_drops_report_progress,
.report_final = hits_drops_report_final,
};
const struct bench bench_strncmp_helper = {
.name = "strncmp-helper",
.validate = strncmp_validate,
.setup = strncmp_helper_setup,
.producer_thread = strncmp_producer,
.consumer_thread = strncmp_consumer,
.measure = strncmp_measure,
.report_progress = hits_drops_report_progress,
.report_final = hits_drops_report_final,
};

12
tools/testing/selftests/bpf/benchs/run_bench_strncmp.sh Executable file
View File

@ -0,0 +1,12 @@
#!/bin/bash
# SPDX-License-Identifier: GPL-2.0
source ./benchs/run_common.sh
set -eufo pipefail
for s in 1 8 64 512 2048 4095; do
for b in no-helper helper; do
summarize ${b}-${s} "$($RUN_BENCH --cmp-str-len=$s strncmp-${b})"
done
done

50
tools/testing/selftests/bpf/progs/strncmp_bench.c Normal file
View File

@ -0,0 +1,50 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2021. Huawei Technologies Co., Ltd */
#include <linux/types.h>
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#define STRNCMP_STR_SZ 4096
/* Will be updated by benchmark before program loading */
const volatile unsigned int cmp_str_len = 1;
const char target[STRNCMP_STR_SZ];
long hits = 0;
char str[STRNCMP_STR_SZ];
char _license[] SEC("license") = "GPL";
static __always_inline int local_strncmp(const char *s1, unsigned int sz,
const char *s2)
{
int ret = 0;
unsigned int i;
for (i = 0; i < sz; i++) {
/* E.g. 0xff > 0x31 */
ret = (unsigned char)s1[i] - (unsigned char)s2[i];
if (ret || !s1[i])
break;
}
return ret;
}
SEC("tp/syscalls/sys_enter_getpgid")
int strncmp_no_helper(void *ctx)
{
if (local_strncmp(str, cmp_str_len + 1, target) < 0)
__sync_add_and_fetch(&hits, 1);
return 0;
}
SEC("tp/syscalls/sys_enter_getpgid")
int strncmp_helper(void *ctx)
{
if (bpf_strncmp(str, cmp_str_len + 1, target) < 0)
__sync_add_and_fetch(&hits, 1);
return 0;
}