Documentation/bpf/map_hash.rst

1 .. SPDX-License-Identifier: GPL-2.0-only
3 .. Copyright (C) 2022-2023 Isovalent, Inc.
10    - ``BPF_MAP_TYPE_HASH`` was introduced in kernel version 3.19
11    - ``BPF_MAP_TYPE_PERCPU_HASH`` was introduced in version 4.6
12    - Both ``BPF_MAP_TYPE_LRU_HASH`` and ``BPF_MAP_TYPE_LRU_PERCPU_HASH``
20 to the max_entries limit that you specify. Hash maps use pre-allocation
22 used to disable pre-allocation when it is too memory expensive.
25 CPU. The per-cpu values are stored internally in an array.
40 **BPF_F_NO_COMMON_LRU**  Per-CPU LRU, global map   Per-CPU LRU, per-cpu map
41 **!BPF_F_NO_COMMON_LRU** Global LRU, global map    Global LRU, per-cpu map
48 ----------
53 .. code-block:: c
61 - ``BPF_ANY`` will create a new element or update an existing element
62 - ``BPF_NOEXIST`` will create a new element only if one did not already
64 - ``BPF_EXIST`` will update an existing element
72 .. code-block:: c
83 .. code-block:: c
92 --------------
101 .. code-block:: c
111 -----------
114 programs running on different CPUs.  Since Kernel version 5.1, the BPF
119 ---------
124 .. code-block:: c
132 current key. ``bpf_map_get_next_key()`` returns 0 on success, -ENOENT if
150 .. code-block:: c
174 .. code-block:: c
184                     __sync_fetch_and_add(&value->packets, 1);
185                     __sync_fetch_and_add(&value->bytes, bytes);
195 .. code-block:: c
228 --------------------------------------
235 - Attempt to use CPU-local state to batch operations
236 - Attempt to fetch free nodes from global lists
237 - Attempt to pull any node from a global list and remove it from the hashmap
238 - Attempt to pull any node from any CPU's list and remove it from the hashmap
244 .. kernel-figure::  map_lru_hash_update.dot
259 properties would be per-cpu.