tools/testing/selftests/bpf/progs/bpf_hashmap_lookup.c

Source file repositories/reference/linux-study-clean/tools/testing/selftests/bpf/progs/bpf_hashmap_lookup.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/bpf/progs/bpf_hashmap_lookup.c
Extension
.c
Size
1545 bytes
Lines
64
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2023 Isovalent */

#include "vmlinux.h"

#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"

char _license[] SEC("license") = "GPL";

struct {
	__uint(type, BPF_MAP_TYPE_HASH);
} hash_map_bench SEC(".maps");

/* The number of slots to store times */
#define NR_SLOTS 32
#define NR_CPUS 256
#define CPU_MASK (NR_CPUS-1)

/* Configured by userspace */
u64 nr_entries;
u64 nr_loops;
u32 __attribute__((__aligned__(8))) key[NR_CPUS];

/* Filled by us */
u64 __attribute__((__aligned__(256))) percpu_times_index[NR_CPUS];
u64 __attribute__((__aligned__(256))) percpu_times[NR_CPUS][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 & CPU_MASK] % NR_SLOTS;
	start_time = bpf_ktime_get_ns();
	bpf_loop(nr_loops, loop_lookup_callback, NULL, 0);
	percpu_times[cpu & CPU_MASK][times_index] = bpf_ktime_get_ns() - start_time;
	percpu_times_index[cpu & CPU_MASK] += 1;
	return 0;
}

Annotation

Implementation Notes