samples/bpf: replace broken overhead microbenchmark with fib_table_lookup

The test_overhead bpf program is designed to compare performance
between tracepoint and kprobe. Initially it used task_rename and
urandom_read tracepoint.

However, commit 14c174633f34 ("random: remove unused tracepoints")
removed urandom_read tracepoint, and for this reason the test_overhead
got broken.

This commit introduces new microbenchmark using fib_table_lookup.
This microbenchmark sends UDP packets to localhost in order to invoke
fib_table_lookup.

In a nutshell:
fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
addr.sin_addr.s_addr = inet_addr(DUMMY_IP);
addr.sin_port = htons(DUMMY_PORT);
for() {
    sendto(fd, buf, strlen(buf), 0,
            (struct sockaddr *)&addr, sizeof(addr));
}

on 4 cpus in parallel:
                                            lookup per sec
base (no tracepoints, no kprobes)               381k
with kprobe at fib_table_lookup()               325k
with tracepoint at fib:fib_table_lookup         330k
with raw_tracepoint at fib:fib_table_lookup     365k

Fixes: 14c174633f34 ("random: remove unused tracepoints")

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Link: https://lore.kernel.org/r/20230115071613.125791-6-danieltimlee@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 19 insertions, 7 deletions

diff --git a/samples/bpf/test_overhead_tp_kern.c b/samples/bpf/test_overhead_tp_kern.c
index 80edadacb692..f170e9b1ea21 100644
--- a/samples/bpf/test_overhead_tp_kern.c
+++ b/samples/bpf/test_overhead_tp_kern.c
@@ -22,15 +22,27 @@ int prog(struct task_rename *ctx)
 	return 0;
 }
 
-/* from /sys/kernel/debug/tracing/events/random/urandom_read/format */
-struct urandom_read {
+/* from /sys/kernel/debug/tracing/events/fib/fib_table_lookup/format */
+struct fib_table_lookup {
 	__u64 pad;
-	int got_bits;
-	int pool_left;
-	int input_left;
+	__u32 tb_id;
+	int err;
+	int oif;
+	int iif;
+	__u8 proto;
+	__u8 tos;
+	__u8 scope;
+	__u8 flags;
+	__u8 src[4];
+	__u8 dst[4];
+	__u8 gw4[4];
+	__u8 gw6[16];
+	__u16 sport;
+	__u16 dport;
+	char name[16];
 };
-SEC("tracepoint/random/urandom_read")
-int prog2(struct urandom_read *ctx)
+SEC("tracepoint/fib/fib_table_lookup")
+int prog2(struct fib_table_lookup *ctx)
 {
 	return 0;
 }