mirror/libbpf
1
0
Fork 0
mirror of https://github.com/netdata/libbpf.git synced 2026-04-06 00:29:07 +08:00
Code Issues Packages Projects Releases Wiki Activity

bpf: Add libbpf logic for user-space ring buffer

Browse Source 
Now that all of the logic is in place in the kernel to support user-space
produced ring buffers, we can add the user-space logic to libbpf. This
patch therefore adds the following public symbols to libbpf:

struct user_ring_buffer *
user_ring_buffer__new(int map_fd,
		      const struct user_ring_buffer_opts *opts);
void *user_ring_buffer__reserve(struct user_ring_buffer *rb, __u32 size);
void *user_ring_buffer__reserve_blocking(struct user_ring_buffer *rb,
                                         __u32 size, int timeout_ms);
void user_ring_buffer__submit(struct user_ring_buffer *rb, void *sample);
void user_ring_buffer__discard(struct user_ring_buffer *rb,
void user_ring_buffer__free(struct user_ring_buffer *rb);

A user-space producer must first create a struct user_ring_buffer * object
with user_ring_buffer__new(), and can then reserve samples in the
ring buffer using one of the following two symbols:

void *user_ring_buffer__reserve(struct user_ring_buffer *rb, __u32 size);
void *user_ring_buffer__reserve_blocking(struct user_ring_buffer *rb,
                                         __u32 size, int timeout_ms);

With user_ring_buffer__reserve(), a pointer to a 'size' region of the ring
buffer will be returned if sufficient space is available in the buffer.
user_ring_buffer__reserve_blocking() provides similar semantics, but will
block for up to 'timeout_ms' in epoll_wait if there is insufficient space
in the buffer. This function has the guarantee from the kernel that it will
receive at least one event-notification per invocation to
bpf_ringbuf_drain(), provided that at least one sample is drained, and the
BPF program did not pass the BPF_RB_NO_WAKEUP flag to bpf_ringbuf_drain().

Once a sample is reserved, it must either be committed to the ring buffer
with user_ring_buffer__submit(), or discarded with
user_ring_buffer__discard().

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220920000100.477320-4-void@manifault.com
This commit is contained in:
David Vernet
2022-09-19 19:00:59 -05:00
committed by Andrii Nakryiko
parent 28903eb40e
commit 9e9bf46c92
6 changed files with 398 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
src/libbpf.c
View File

@@ -2373,6 +2373,12 @@ static size_t adjust_ringbuf_sz(size_t sz)
return sz;
}
static bool map_is_ringbuf(const struct bpf_map *map)
{
return map->def.type == BPF_MAP_TYPE_RINGBUF ||
map->def.type == BPF_MAP_TYPE_USER_RINGBUF;
}
static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def)
{
map->def.type = def->map_type;
@@ -2387,7 +2393,7 @@ static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def
map->btf_value_type_id = def->value_type_id;
/* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
if (map->def.type == BPF_MAP_TYPE_RINGBUF)
if (map_is_ringbuf(map))
map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);
if (def->parts & MAP_DEF_MAP_TYPE)
@@ -4370,7 +4376,7 @@ int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries)
map->def.max_entries = max_entries;
/* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
if (map->def.type == BPF_MAP_TYPE_RINGBUF)
if (map_is_ringbuf(map))
map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);
return 0;