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From: Brian Vazquez <brianvv@google.com>
To: Brian Vazquez <brianvv.kernel@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S . Miller" <davem@davemloft.net>
Cc: Stanislav Fomichev <sdf@google.com>,
	Willem de Bruijn <willemb@google.com>,
	Petar Penkov <ppenkov@google.com>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	bpf@vger.kernel.org, Brian Vazquez <brianvv@google.com>
Subject: [PATCH bpf-next 0/6] bpf: add BPF_MAP_DUMP command to dump more than one entry per call
Date: Wed, 24 Jul 2019 09:57:57 -0700
Message-ID: <20190724165803.87470-1-brianvv@google.com> (raw)

This introduces a new command to retrieve multiple 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

Note that this implementation can be extended later to do dump and
delete by extending map_lookup_and_delete_elem (currently it only works
for bpf queue/stack maps) and either use a new flag in map_dump or a new
command map_dump_and_delete. 

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:       69038725 entry-by-entry: 112384424 improvement
38.569134
buf_len_2:       40897447 entry-by-entry: 111030546 improvement
63.165590
buf_len_230:     13652714 entry-by-entry: 111694058 improvement
87.776687
buf_len_5000:    13576271 entry-by-entry: 111101169 improvement
87.780263
buf_len_73000:   14694343 entry-by-entry: 111740162 improvement
86.849542
buf_len_100000:  13745969 entry-by-entry: 114151991 improvement
87.958187
buf_len_234567:  14329834 entry-by-entry: 114427589 improvement
87.476941

The series of patches are split as follows:

- First patch move some map_lookup_elem logic into 2 fucntions to
deduplicate code: bpf_map_value_size and bpf_map_copy_value
- Second patch introduce map_dump function
- Third patch syncs tools linux headers
- Fourth patch adds libbpf support
- Last two patches adds tests

RFC Changelog:

- remove wrong usage of attr.flags
- move map_fd to remove hole after it

v3:
- add explanation of the API in the commit message
- fix masked errors and return them to user
- copy last_key from return buf into prev_key if it was provided
- run perf test with kpti and retpoline mitigations

v2:
- use proper bpf-next tag

Brian Vazquez (6):
  bpf: add bpf_map_value_size and bp_map_copy_value helper functions
  bpf: add BPF_MAP_DUMP command to dump 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                    | 251 ++++++++++++++++++------
 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 | 148 +++++++++++++-
 7 files changed, 388 insertions(+), 63 deletions(-)

-- 
2.22.0.657.g960e92d24f-goog


             reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-24 16:57 Brian Vazquez [this message]
2019-07-24 16:57 ` [PATCH bpf-next 1/6] bpf: add bpf_map_value_size and bp_map_copy_value helper functions Brian Vazquez
2019-07-24 20:53   ` Song Liu
2019-07-24 16:57 ` [PATCH bpf-next 2/6] bpf: add BPF_MAP_DUMP command to dump more than one entry per call Brian Vazquez
2019-07-24 19:54   ` Willem de Bruijn
2019-07-24 22:26     ` Brian Vazquez
2019-07-24 22:33       ` Willem de Bruijn
2019-07-24 21:40   ` Song Liu
2019-07-24 22:44     ` Brian Vazquez
2019-07-24 23:04       ` Song Liu
2019-07-25 23:25         ` Brian Vazquez
2019-07-25 23:54           ` Alexei Starovoitov
2019-07-26  1:02             ` Willem de Bruijn
2019-07-26  1:24             ` Brian Vazquez
2019-07-26  1:47               ` Alexei Starovoitov
2019-07-26  6:10                 ` Yonghong Song
2019-07-26 23:36                   ` Brian Vazquez
2019-07-27  0:02                     ` Jakub Kicinski
2019-07-27 17:54                     ` Yonghong Song
2019-07-24 16:58 ` [PATCH bpf-next 3/6] bpf: keep bpf.h in sync with tools/ Brian Vazquez
2019-07-24 21:41   ` Song Liu
2019-07-24 23:10   ` Andrii Nakryiko
2019-07-25 23:27     ` Brian Vazquez
2019-07-24 16:58 ` [PATCH bpf-next 4/6] libbpf: support BPF_MAP_DUMP command Brian Vazquez
2019-07-24 19:51   ` Willem de Bruijn
2019-07-24 16:58 ` [PATCH bpf-next 5/6] selftests/bpf: test BPF_MAP_DUMP command on a bpf hashmap Brian Vazquez
2019-07-24 21:58   ` Song Liu
2019-07-24 16:58 ` [PATCH bpf-next 6/6] selftests/bpf: add test to measure performance of BPF_MAP_DUMP Brian Vazquez
2019-07-24 22:01   ` Song Liu
2019-07-24 19:20 ` [PATCH bpf-next 0/6] bpf: add BPF_MAP_DUMP command to dump more than one entry per call Song Liu
2019-07-24 22:15   ` Brian Vazquez

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