Commit 95ff141e authored Mar 15, 2017 by Alexei Starovoitov Committed by David S. Miller Mar 16, 2017

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>

parent 9015d2f5

samples/bpf/map_perf_test_kern.c

+33 −0

Original line number	Diff line number	Diff line
		@@ -65,6 +65,13 @@ struct bpf_map_def SEC("maps") lpm_trie_map_alloc = {
		.map_flags = BPF_F_NO_PREALLOC,
		};

		struct bpf_map_def SEC("maps") array_map = {
		.type = BPF_MAP_TYPE_ARRAY,
		.key_size = sizeof(u32),
		.value_size = sizeof(long),
		.max_entries = MAX_ENTRIES,
		};

		SEC("kprobe/sys_getuid")
		int stress_hmap(struct pt_regs *ctx)
		{
		@@ -165,5 +172,31 @@ int stress_lpm_trie_map_alloc(struct pt_regs *ctx)
		return 0;
		}

		SEC("kprobe/sys_getpgid")
		int stress_hash_map_lookup(struct pt_regs *ctx)
		{
		u32 key = 1, i;
		long *value;

		#pragma clang loop unroll(full)
		for (i = 0; i < 64; ++i)
		value = bpf_map_lookup_elem(&hash_map, &key);

		return 0;
		}

		SEC("kprobe/sys_getpgrp")
		int stress_array_map_lookup(struct pt_regs *ctx)
		{
		u32 key = 1, i;
		long *value;

		#pragma clang loop unroll(full)
		for (i = 0; i < 64; ++i)
		value = bpf_map_lookup_elem(&array_map, &key);

		return 0;
		}

		char _license[] SEC("license") = "GPL";
		u32 _version SEC("version") = LINUX_VERSION_CODE;

samples/bpf/map_perf_test_user.c

+32 −0

Original line number	Diff line number	Diff line
		@@ -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)