samples/bpf: add map_lookup microbenchmark
$ map_perf_test 128
speed of HASH bpf_map_lookup_elem() in lookups per second
w/o JIT w/JIT
before 46M 58M
after 42M 74M
perf report
before:
54.23% map_perf_test [kernel.kallsyms] [k] __htab_map_lookup_elem
14.24% map_perf_test [kernel.kallsyms] [k] lookup_elem_raw
8.84% map_perf_test [kernel.kallsyms] [k] htab_map_lookup_elem
5.93% map_perf_test [kernel.kallsyms] [k] bpf_map_lookup_elem
2.30% map_perf_test [kernel.kallsyms] [k] bpf_prog_da4fc6a3f41761a2
1.49% map_perf_test [kernel.kallsyms] [k] kprobe_ftrace_handler
after:
60.03% map_perf_test [kernel.kallsyms] [k] __htab_map_lookup_elem
18.07% map_perf_test [kernel.kallsyms] [k] lookup_elem_raw
2.91% map_perf_test [kernel.kallsyms] [k] bpf_prog_da4fc6a3f41761a2
1.94% map_perf_test [kernel.kallsyms] [k] _einittext
1.90% map_perf_test [kernel.kallsyms] [k] __audit_syscall_exit
1.72% map_perf_test [kernel.kallsyms] [k] kprobe_ftrace_handler
Notice that bpf_map_lookup_elem() and htab_map_lookup_elem() are trivial
functions, yet they take sizeable amount of cpu time.
htab_map_gen_lookup() removes bpf_map_lookup_elem() and converts
htab_map_lookup_elem() into three BPF insns which causing cpu time
for bpf_prog_da4fc6a3f41761a2() slightly increase.
$ map_perf_test 256
speed of ARRAY bpf_map_lookup_elem() in lookups per second
w/o JIT w/JIT
before 97M 174M
after 64M 280M
before:
37.33% map_perf_test [kernel.kallsyms] [k] array_map_lookup_elem
13.95% map_perf_test [kernel.kallsyms] [k] bpf_map_lookup_elem
6.54% map_perf_test [kernel.kallsyms] [k] bpf_prog_da4fc6a3f41761a2
4.57% map_perf_test [kernel.kallsyms] [k] kprobe_ftrace_handler
after:
32.86% map_perf_test [kernel.kallsyms] [k] bpf_prog_da4fc6a3f41761a2
6.54% map_perf_test [kernel.kallsyms] [k] kprobe_ftrace_handler
array_map_gen_lookup() removes calls to array_map_lookup_elem()
and bpf_map_lookup_elem() and replaces them with 7 bpf insns.
The performance without JIT is slower, since executing extra insns
in the interpreter is slower than running native C code,
but with JIT the performance gains are obvious,
since native C->x86 code is replaced with fewer bpf->x86 instructions.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/samples/bpf/map_perf_test_user.c b/samples/bpf/map_perf_test_user.c
index 680260a..e29ff31 100644
--- a/samples/bpf/map_perf_test_user.c
+++ b/samples/bpf/map_perf_test_user.c
@@ -38,6 +38,8 @@ static __u64 time_get_ns(void)
#define LRU_HASH_PREALLOC (1 << 4)
#define PERCPU_LRU_HASH_PREALLOC (1 << 5)
#define LPM_KMALLOC (1 << 6)
+#define HASH_LOOKUP (1 << 7)
+#define ARRAY_LOOKUP (1 << 8)
static int test_flags = ~0;
@@ -125,6 +127,30 @@ static void test_lpm_kmalloc(int cpu)
cpu, MAX_CNT * 1000000000ll / (time_get_ns() - start_time));
}
+static void test_hash_lookup(int cpu)
+{
+ __u64 start_time;
+ int i;
+
+ start_time = time_get_ns();
+ for (i = 0; i < MAX_CNT; i++)
+ syscall(__NR_getpgid, 0);
+ printf("%d:hash_lookup %lld lookups per sec\n",
+ cpu, MAX_CNT * 1000000000ll * 64 / (time_get_ns() - start_time));
+}
+
+static void test_array_lookup(int cpu)
+{
+ __u64 start_time;
+ int i;
+
+ start_time = time_get_ns();
+ for (i = 0; i < MAX_CNT; i++)
+ syscall(__NR_getpgrp, 0);
+ printf("%d:array_lookup %lld lookups per sec\n",
+ cpu, MAX_CNT * 1000000000ll * 64 / (time_get_ns() - start_time));
+}
+
static void loop(int cpu)
{
cpu_set_t cpuset;
@@ -153,6 +179,12 @@ static void loop(int cpu)
if (test_flags & LPM_KMALLOC)
test_lpm_kmalloc(cpu);
+
+ if (test_flags & HASH_LOOKUP)
+ test_hash_lookup(cpu);
+
+ if (test_flags & ARRAY_LOOKUP)
+ test_array_lookup(cpu);
}
static void run_perf_test(int tasks)