diff options
author | Andrii Nakryiko <andrii@kernel.org> | 2021-11-16 04:30:41 +0300 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2021-11-16 16:46:49 +0300 |
commit | d41bc48bfab2076f7db88d079a3a3203dd9c4a54 (patch) | |
tree | a498bb26f6d16d4e00cada646a8fe6fd1f6687f4 /tools | |
parent | ebf7f6f0a6cdcc17a3da52b81e4b3a98c4005028 (diff) | |
download | linux-d41bc48bfab2076f7db88d079a3a3203dd9c4a54.tar.xz |
selftests/bpf: Add uprobe triggering overhead benchmarks
Add benchmark to measure overhead of uprobes and uretprobes. Also have
a baseline (no uprobe attached) benchmark.
On my dev machine, baseline benchmark can trigger 130M user_target()
invocations. When uprobe is attached, this falls to just 700K. With
uretprobe, we get down to 520K:
$ sudo ./bench trig-uprobe-base -a
Summary: hits 131.289 ± 2.872M/s
# UPROBE
$ sudo ./bench -a trig-uprobe-without-nop
Summary: hits 0.729 ± 0.007M/s
$ sudo ./bench -a trig-uprobe-with-nop
Summary: hits 1.798 ± 0.017M/s
# URETPROBE
$ sudo ./bench -a trig-uretprobe-without-nop
Summary: hits 0.508 ± 0.012M/s
$ sudo ./bench -a trig-uretprobe-with-nop
Summary: hits 0.883 ± 0.008M/s
So there is almost 2.5x performance difference between probing nop vs
non-nop instruction for entry uprobe. And 1.7x difference for uretprobe.
This means that non-nop uprobe overhead is around 1.4 microseconds for uprobe
and 2 microseconds for non-nop uretprobe.
For nop variants, uprobe and uretprobe overhead is down to 0.556 and
1.13 microseconds, respectively.
For comparison, just doing a very low-overhead syscall (with no BPF
programs attached anywhere) gives:
$ sudo ./bench trig-base -a
Summary: hits 4.830 ± 0.036M/s
So uprobes are about 2.67x slower than pure context switch.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211116013041.4072571-1-andrii@kernel.org
Diffstat (limited to 'tools')
-rw-r--r-- | tools/testing/selftests/bpf/Makefile | 4 | ||||
-rw-r--r-- | tools/testing/selftests/bpf/bench.c | 10 | ||||
-rw-r--r-- | tools/testing/selftests/bpf/benchs/bench_trigger.c | 146 | ||||
-rw-r--r-- | tools/testing/selftests/bpf/progs/trigger_bench.c | 7 |
4 files changed, 166 insertions, 1 deletions
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index 0470802c907c..35684d61aaeb 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -533,7 +533,9 @@ $(OUTPUT)/bench_ringbufs.o: $(OUTPUT)/ringbuf_bench.skel.h \ $(OUTPUT)/bench_bloom_filter_map.o: $(OUTPUT)/bloom_filter_bench.skel.h $(OUTPUT)/bench.o: bench.h testing_helpers.h $(BPFOBJ) $(OUTPUT)/bench: LDLIBS += -lm -$(OUTPUT)/bench: $(OUTPUT)/bench.o $(OUTPUT)/testing_helpers.o \ +$(OUTPUT)/bench: $(OUTPUT)/bench.o \ + $(OUTPUT)/testing_helpers.o \ + $(OUTPUT)/trace_helpers.o \ $(OUTPUT)/bench_count.o \ $(OUTPUT)/bench_rename.o \ $(OUTPUT)/bench_trigger.o \ diff --git a/tools/testing/selftests/bpf/bench.c b/tools/testing/selftests/bpf/bench.c index cc4722f693e9..c75e7ee28746 100644 --- a/tools/testing/selftests/bpf/bench.c +++ b/tools/testing/selftests/bpf/bench.c @@ -359,6 +359,11 @@ extern const struct bench bench_trig_kprobe; extern const struct bench bench_trig_fentry; extern const struct bench bench_trig_fentry_sleep; extern const struct bench bench_trig_fmodret; +extern const struct bench bench_trig_uprobe_base; +extern const struct bench bench_trig_uprobe_with_nop; +extern const struct bench bench_trig_uretprobe_with_nop; +extern const struct bench bench_trig_uprobe_without_nop; +extern const struct bench bench_trig_uretprobe_without_nop; extern const struct bench bench_rb_libbpf; extern const struct bench bench_rb_custom; extern const struct bench bench_pb_libbpf; @@ -385,6 +390,11 @@ static const struct bench *benchs[] = { &bench_trig_fentry, &bench_trig_fentry_sleep, &bench_trig_fmodret, + &bench_trig_uprobe_base, + &bench_trig_uprobe_with_nop, + &bench_trig_uretprobe_with_nop, + &bench_trig_uprobe_without_nop, + &bench_trig_uretprobe_without_nop, &bench_rb_libbpf, &bench_rb_custom, &bench_pb_libbpf, diff --git a/tools/testing/selftests/bpf/benchs/bench_trigger.c b/tools/testing/selftests/bpf/benchs/bench_trigger.c index f41a491a8cc0..049a5ad56f65 100644 --- a/tools/testing/selftests/bpf/benchs/bench_trigger.c +++ b/tools/testing/selftests/bpf/benchs/bench_trigger.c @@ -2,6 +2,7 @@ /* Copyright (c) 2020 Facebook */ #include "bench.h" #include "trigger_bench.skel.h" +#include "trace_helpers.h" /* BPF triggering benchmarks */ static struct trigger_ctx { @@ -107,6 +108,101 @@ static void *trigger_consumer(void *input) return NULL; } +/* make sure call is not inlined and not avoided by compiler, so __weak and + * inline asm volatile in the body of the function + * + * There is a performance difference between uprobing at nop location vs other + * instructions. So use two different targets, one of which starts with nop + * and another doesn't. + * + * GCC doesn't generate stack setup preample for these functions due to them + * having no input arguments and doing nothing in the body. + */ +__weak void uprobe_target_with_nop(void) +{ + asm volatile ("nop"); +} + +__weak void uprobe_target_without_nop(void) +{ + asm volatile (""); +} + +static void *uprobe_base_producer(void *input) +{ + while (true) { + uprobe_target_with_nop(); + atomic_inc(&base_hits.value); + } + return NULL; +} + +static void *uprobe_producer_with_nop(void *input) +{ + while (true) + uprobe_target_with_nop(); + return NULL; +} + +static void *uprobe_producer_without_nop(void *input) +{ + while (true) + uprobe_target_without_nop(); + return NULL; +} + +static void usetup(bool use_retprobe, bool use_nop) +{ + size_t uprobe_offset; + ssize_t base_addr; + struct bpf_link *link; + + setup_libbpf(); + + ctx.skel = trigger_bench__open_and_load(); + if (!ctx.skel) { + fprintf(stderr, "failed to open skeleton\n"); + exit(1); + } + + base_addr = get_base_addr(); + if (use_nop) + uprobe_offset = get_uprobe_offset(&uprobe_target_with_nop, base_addr); + else + uprobe_offset = get_uprobe_offset(&uprobe_target_without_nop, base_addr); + + link = bpf_program__attach_uprobe(ctx.skel->progs.bench_trigger_uprobe, + use_retprobe, + -1 /* all PIDs */, + "/proc/self/exe", + uprobe_offset); + if (!link) { + fprintf(stderr, "failed to attach uprobe!\n"); + exit(1); + } + ctx.skel->links.bench_trigger_uprobe = link; +} + +static void uprobe_setup_with_nop() +{ + usetup(false, true); +} + +static void uretprobe_setup_with_nop() +{ + usetup(true, true); +} + +static void uprobe_setup_without_nop() +{ + usetup(false, false); +} + +static void uretprobe_setup_without_nop() +{ + usetup(true, false); +} + const struct bench bench_trig_base = { .name = "trig-base", .validate = trigger_validate, @@ -182,3 +278,53 @@ const struct bench bench_trig_fmodret = { .report_progress = hits_drops_report_progress, .report_final = hits_drops_report_final, }; + +const struct bench bench_trig_uprobe_base = { + .name = "trig-uprobe-base", + .setup = NULL, /* no uprobe/uretprobe is attached */ + .producer_thread = uprobe_base_producer, + .consumer_thread = trigger_consumer, + .measure = trigger_base_measure, + .report_progress = hits_drops_report_progress, + .report_final = hits_drops_report_final, +}; + +const struct bench bench_trig_uprobe_with_nop = { + .name = "trig-uprobe-with-nop", + .setup = uprobe_setup_with_nop, + .producer_thread = uprobe_producer_with_nop, + .consumer_thread = trigger_consumer, + .measure = trigger_measure, + .report_progress = hits_drops_report_progress, + .report_final = hits_drops_report_final, +}; + +const struct bench bench_trig_uretprobe_with_nop = { + .name = "trig-uretprobe-with-nop", + .setup = uretprobe_setup_with_nop, + .producer_thread = uprobe_producer_with_nop, + .consumer_thread = trigger_consumer, + .measure = trigger_measure, + .report_progress = hits_drops_report_progress, + .report_final = hits_drops_report_final, +}; + +const struct bench bench_trig_uprobe_without_nop = { + .name = "trig-uprobe-without-nop", + .setup = uprobe_setup_without_nop, + .producer_thread = uprobe_producer_without_nop, + .consumer_thread = trigger_consumer, + .measure = trigger_measure, + .report_progress = hits_drops_report_progress, + .report_final = hits_drops_report_final, +}; + +const struct bench bench_trig_uretprobe_without_nop = { + .name = "trig-uretprobe-without-nop", + .setup = uretprobe_setup_without_nop, + .producer_thread = uprobe_producer_without_nop, + .consumer_thread = trigger_consumer, + .measure = trigger_measure, + .report_progress = hits_drops_report_progress, + .report_final = hits_drops_report_final, +}; diff --git a/tools/testing/selftests/bpf/progs/trigger_bench.c b/tools/testing/selftests/bpf/progs/trigger_bench.c index 9a4d09590b3d..2098f3f27f18 100644 --- a/tools/testing/selftests/bpf/progs/trigger_bench.c +++ b/tools/testing/selftests/bpf/progs/trigger_bench.c @@ -52,3 +52,10 @@ int bench_trigger_fmodret(void *ctx) __sync_add_and_fetch(&hits, 1); return -22; } + +SEC("uprobe/self/uprobe_target") +int bench_trigger_uprobe(void *ctx) +{ + __sync_add_and_fetch(&hits, 1); + return 0; +} |