Re: [PATCH bpf-next 6/6] selftest/bpf/benchs: Add benchmark for hashmap lookups

[Martin KaFai Lau <martin.lau@linux.dev>]

On 1/27/23 10:14 AM, Anton Protopopov wrote:
> +/* The number of slots to store times */
> +#define NR_SLOTS 32
> +
> +/* Configured by userspace */
> +u64 nr_entries;
> +u64 nr_loops;
> +u32 __attribute__((__aligned__(8))) key[256];
> +
> +/* Filled by us */
> +u64 __attribute__((__aligned__(256))) percpu_times_index[NR_SLOTS]; > +u64 __attribute__((__aligned__(256))) percpu_times[256][NR_SLOTS];
> +
> +static inline void patch_key(u32 i)
> +{
> +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
> +	key[0] = i + 1;
> +#else
> +	key[0] = __builtin_bswap32(i + 1);
> +#endif
> +	/* the rest of key is random and is configured by userspace */
> +}
> +
> +static int lookup_callback(__u32 index, u32 *unused)
> +{
> +	patch_key(index);
> +	return bpf_map_lookup_elem(&hash_map_bench, key) ? 0 : 1;
> +}
> +
> +static int loop_lookup_callback(__u32 index, u32 *unused)
> +{
> +	return bpf_loop(nr_entries, lookup_callback, NULL, 0) ? 0 : 1;
> +}
> +
> +SEC("fentry/" SYS_PREFIX "sys_getpgid")
> +int benchmark(void *ctx)
> +{
> +	u32 cpu = bpf_get_smp_processor_id();
> +	u32 times_index;
> +	u64 start_time;
> +
> +	times_index = percpu_times_index[cpu & 255] % NR_SLOTS;

percpu_times_index only has NR_SLOTS (32) elements?

> +	start_time = bpf_ktime_get_ns();
> +	bpf_loop(nr_loops, loop_lookup_callback, NULL, 0);
> +	percpu_times[cpu & 255][times_index] = bpf_ktime_get_ns() - start_time;
> +	percpu_times_index[cpu & 255] += 1;
> +	return 0;
> +}