[PATCH v4 bpf-next 0/9] add bpf batch ops to process more than 1 elem

Brian Vazquez
2020-01-14T16:46:37Z

This patch series introduce batch ops that can be added to bpf maps to
lookup/lookup_and_delete/update/delete more than 1 element at the time,
this is specially useful when syscall overhead is a problem and in case
of hmap it will provide a reliable way of traversing them.

The implementation inclues a generic approach that could potentially be
used by any bpf map and adds it to arraymap, it also includes the specific
implementation of hashmaps which are traversed using buckets instead
of keys.

The bpf syscall subcommands introduced are:

BPF_MAP_LOOKUP_BATCH
BPF_MAP_LOOKUP_AND_DELETE_BATCH
BPF_MAP_UPDATE_BATCH
BPF_MAP_DELETE_BATCH

The UAPI attribute is:

struct { /* struct used by BPF_MAP_*_BATCH commands */
__aligned_u64 in_batch; /* start batch,
* NULL to start from beginning
*/
__aligned_u64 out_batch; /* output: next start batch */
__aligned_u64 keys;
__aligned_u64 values;
__u32 count; /* input/output:
* input: # of key/value
* elements
* output: # of filled elements
*/
__u32 map_fd;
__u64 elem_flags;
__u64 flags;
} batch;

in_batch and out_batch are only used for lookup and lookup_and_delete since
those are the only two operations that attempt to traverse the map.

update/delete batch ops should provide the keys/values that user wants
to modify.

Here are the previous discussions on the batch processing:
- https://lore.kernel.org/bpf/20190724165803.87470-1-brianvv@google.com/
- https://lore.kernel.org/bpf/20190829064502.2750303-1-yhs@fb.com/
- https://lore.kernel.org/bpf/20190906225434.3635421-1-yhs@fb.com/

Changelog sinve v3:
- Do not use copy_to_user inside atomic region (Yonghong Song)
- Use _opts approach on libbpf APIs (Andrii Nakryiko)
- Drop generic_map_lookup_and_delete_batch support
- Free malloc-ed memory in tests (Yonghong Song)
- Reverse christmas tree (Yonghong Song)
- Add acked labels

Changelog sinve v2:
- Add generic batch support for lpm_trie and test it (Yonghong Song)
- Use define MAP_LOOKUP_RETRIES for retries (John Fastabend)
- Return errors directly and remove labels (Yonghong Song)
- Insert new API functions into libbpf alphabetically (Yonghong Song)
- Change hlist_nulls_for_each_entry_rcu to
hlist_nulls_for_each_entry_safe in htab batch ops (Yonghong Song)

Changelog since v1:
- Fix SOB ordering and remove Co-authored-by tag (Alexei Starovoitov)

Changelog since RFC:
- Change batch to in_batch and out_batch to support more flexible opaque
values to iterate the bpf maps.
- Remove update/delete specific batch ops for htab and use the generic
implementations instead.

Brian Vazquez (5):
bpf: add bpf_map_{value_size,update_value,map_copy_value} functions
bpf: add generic support for lookup batch op
bpf: add generic support for update and delete batch ops
bpf: add lookup and update batch ops to arraymap
selftests/bpf: add batch ops testing to array bpf map

Yonghong Song (4):
bpf: add batch ops to all htab bpf map
tools/bpf: sync uapi header bpf.h
libbpf: add libbpf support to batch ops
selftests/bpf: add batch ops testing for htab and htab_percpu map

include/linux/bpf.h | 18 +
include/uapi/linux/bpf.h | 21 +
kernel/bpf/arraymap.c | 2 +
kernel/bpf/hashtab.c | 258 +++++++++
kernel/bpf/syscall.c | 548 ++++++++++++++----
tools/include/uapi/linux/bpf.h | 21 +
tools/lib/bpf/bpf.c | 60 ++
tools/lib/bpf/bpf.h | 22 +
tools/lib/bpf/libbpf.map | 4 +
.../bpf/map_tests/array_map_batch_ops.c | 131 +++++
.../bpf/map_tests/htab_map_batch_ops.c | 285 +++++++++
11 files changed, 1242 insertions(+), 128 deletions(-)
create mode 100644 tools/testing/selftests/bpf/map_tests/array_map_batch_ops.c
create mode 100644 tools/testing/selftests/bpf/map_tests/htab_map_batch_ops.c

--
2.25.0.rc1.283.g88dfdc4193-goog