[PATCH bpf-next 4/5] samples/bpf: Reduce syscall overhead in map_perf_test.

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

From: Alexei Starovoitov <ast@kernel.org>

Make map_perf_test for preallocated and non-preallocated hash map
spend more time inside bpf program to focus performance analysis
on the speed of update/lookup/delete operations performed by bpf program.

It makes 'perf report' of bpf_mem_alloc look like:
 11.76%  map_perf_test    [k] _raw_spin_lock_irqsave
 11.26%  map_perf_test    [k] htab_map_update_elem
  9.70%  map_perf_test    [k] _raw_spin_lock
  9.47%  map_perf_test    [k] htab_map_delete_elem
  8.57%  map_perf_test    [k] memcpy_erms
  5.58%  map_perf_test    [k] alloc_htab_elem
  4.09%  map_perf_test    [k] __htab_map_lookup_elem
  3.44%  map_perf_test    [k] syscall_exit_to_user_mode
  3.13%  map_perf_test    [k] lookup_nulls_elem_raw
  3.05%  map_perf_test    [k] migrate_enable
  3.04%  map_perf_test    [k] memcmp
  2.67%  map_perf_test    [k] unit_free
  2.39%  map_perf_test    [k] lookup_elem_raw

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 samples/bpf/map_perf_test_kern.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/samples/bpf/map_perf_test_kern.c b/samples/bpf/map_perf_test_kern.c
index 8773f22b6a98..d5af4df9d403 100644
--- a/samples/bpf/map_perf_test_kern.c
+++ b/samples/bpf/map_perf_test_kern.c
@@ -108,11 +108,14 @@ int stress_hmap(struct pt_regs *ctx)
 	u32 key = bpf_get_current_pid_tgid();
 	long init_val = 1;
 	long *value;
+	int i;
 
-	bpf_map_update_elem(&hash_map, &key, &init_val, BPF_ANY);
-	value = bpf_map_lookup_elem(&hash_map, &key);
-	if (value)
-		bpf_map_delete_elem(&hash_map, &key);
+	for (i = 0; i < 30; i++) {
+		bpf_map_update_elem(&hash_map, &key, &init_val, BPF_ANY);
+		value = bpf_map_lookup_elem(&hash_map, &key);
+		if (value)
+			bpf_map_delete_elem(&hash_map, &key);
+	}
 
 	return 0;
 }
@@ -137,11 +140,14 @@ int stress_hmap_alloc(struct pt_regs *ctx)
 	u32 key = bpf_get_current_pid_tgid();
 	long init_val = 1;
 	long *value;
+	int i;
 
-	bpf_map_update_elem(&hash_map_alloc, &key, &init_val, BPF_ANY);
-	value = bpf_map_lookup_elem(&hash_map_alloc, &key);
-	if (value)
-		bpf_map_delete_elem(&hash_map_alloc, &key);
+	for (i = 0; i < 30; i++) {
+		bpf_map_update_elem(&hash_map_alloc, &key, &init_val, BPF_ANY);
+		value = bpf_map_lookup_elem(&hash_map_alloc, &key);
+		if (value)
+			bpf_map_delete_elem(&hash_map_alloc, &key);
+	}
 	return 0;
 }
 
-- 
2.30.2