selftests/bpf: Set the default value of consumer_cnt as 0

Considering that only bench_ringbufs.c supports consumer, just set the
default value of consumer_cnt as 0. After that, update the validity
check of consumer_cnt, remove unused consumer_thread code snippets and
set consumer_cnt as 1 in run_bench_ringbufs.sh accordingly.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20230613080921.1623219-5-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftest/bpf/benchs: Add benchmark for hashmap lookups

Add a new benchmark which measures hashmap lookup operations speed. A user can
control the following parameters of the benchmark:

* key_size (max 1024): the key size to use
* max_entries: the hashmap max entries
* nr_entries: the number of entries to insert/lookup
* nr_loops: the number of loops for the benchmark
* map_flags The hashmap flags passed to BPF_MAP_CREATE

The BPF program performing the benchmarks calls two nested bpf_loop:

bpf_loop(nr_loops/nr_entries)
bpf_loop(nr_entries)
bpf_map_lookup()

So the nr_loops determines the number of actual map lookups. All lookups are
successful.

Example (the output is generated on a AMD Ryzen 9 3950X machine):

for nr_entries in `seq 4096 4096 65536`; do echo -n "$((nr_entries*100/65536))% full: "; sudo ./bench -d2 -a bpf-hashmap-lookup --key_size=4 --nr_entries=$nr_entries --max_entries=65536 --nr_loops=1000000 --map_flags=0x40 | grep cpu; done
6% full: cpu01: lookup 50.739M ± 0.018M events/sec (approximated from 32 samples of ~19ms)
12% full: cpu01: lookup 47.751M ± 0.015M events/sec (approximated from 32 samples of ~20ms)
18% full: cpu01: lookup 45.153M ± 0.013M events/sec (approximated from 32 samples of ~22ms)
25% full: cpu01: lookup 43.826M ± 0.014M events/sec (approximated from 32 samples of ~22ms)
31% full: cpu01: lookup 41.971M ± 0.012M events/sec (approximated from 32 samples of ~23ms)
37% full: cpu01: lookup 41.034M ± 0.015M events/sec (approximated from 32 samples of ~24ms)
43% full: cpu01: lookup 39.946M ± 0.012M events/sec (approximated from 32 samples of ~25ms)
50% full: cpu01: lookup 38.256M ± 0.014M events/sec (approximated from 32 samples of ~26ms)
56% full: cpu01: lookup 36.580M ± 0.018M events/sec (approximated from 32 samples of ~27ms)
62% full: cpu01: lookup 36.252M ± 0.012M events/sec (approximated from 32 samples of ~27ms)
68% full: cpu01: lookup 35.200M ± 0.012M events/sec (approximated from 32 samples of ~28ms)
75% full: cpu01: lookup 34.061M ± 0.009M events/sec (approximated from 32 samples of ~29ms)
81% full: cpu01: lookup 34.374M ± 0.010M events/sec (approximated from 32 samples of ~29ms)
87% full: cpu01: lookup 33.244M ± 0.011M events/sec (approximated from 32 samples of ~30ms)
93% full: cpu01: lookup 32.182M ± 0.013M events/sec (approximated from 32 samples of ~31ms)
100% full: cpu01: lookup 31.497M ± 0.016M events/sec (approximated from 32 samples of ~31ms)

Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230213091519.1202813-8-aspsk@isovalent.com