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Subject[RFC PATCH 0/6] bpf: add BPF_MAP_DUMP command to access more
From
This introduces a new command to retrieve a variable number of entries
from a bpf map.

This new command can be executed from the existing BPF syscall as follows:

err = bpf(BPF_MAP_DUMP, union bpf_attr *attr, u32 size)
using attr->dump.map_fd, attr->dump.prev_key, attr->dump.buf,
attr->dump.buf_len
returns zero or negative error, and populates buf and buf_len on
succees

This implementation is wrapping the existing bpf methods:
map_get_next_key and map_lookup_elem
the results show that even with a 1-elem_size buffer, it runs ~40 faster
than the current implementation, improvements of ~85% are reported when
the buffer size is increased, although, after the buffer size is around
5% of the total number of entries there's no huge difference in increasing
it.

Tested:
Tried different size buffers to handle case where the bulk is bigger, or
the elements to retrieve are less than the existing ones, all runs read
a map of 100K entries. Below are the results(in ns) from the different
runs:

buf_len_1: 55528939 entry-by-entry: 97244981 improvement 42.897887%
buf_len_2: 34425779 entry-by-entry: 88863122 improvement 61.259769%
buf_len_230: 11700316 entry-by-entry: 88753301 improvement 86.817036%
buf_len_5000: 11615290 entry-by-entry: 88362637 improvement 86.854976%
buf_len_73000: 12083976 entry-by-entry: 89956483 improvement 86.566865%
buf_len_100000: 12638913 entry-by-entry: 89642303 improvement 85.900727%
buf_len_234567: 11873964 entry-by-entry: 89080077 improvement 86.670461%

Suggested-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Brian Vazquez <brianvv@google.com>

Brian Vazquez (6):
bpf: add bpf_map_value_size and bp_map_copy_value helper functions
bpf: add BPF_MAP_DUMP command to access more than one entry per call
bpf: keep bpf.h in sync with tools/
libbpf: support BPF_MAP_DUMP command
selftests/bpf: test BPF_MAP_DUMP command on a bpf hashmap
selftests/bpf: add test to measure performance of BPF_MAP_DUMP

include/uapi/linux/bpf.h | 9 +
kernel/bpf/syscall.c | 242 ++++++++++++++++++------
tools/include/uapi/linux/bpf.h | 9 +
tools/lib/bpf/bpf.c | 28 +++
tools/lib/bpf/bpf.h | 4 +
tools/lib/bpf/libbpf.map | 2 +
tools/testing/selftests/bpf/test_maps.c | 141 +++++++++++++-
7 files changed, 372 insertions(+), 63 deletions(-)

--
2.22.0.410.gd8fdbe21b5-goog

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