netdev - [PATCH bpf-next 0/3] bpf: implement percpu map pretty print for bpffs and bpftool

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Date:   Wed, 29 Aug 2018 14:43:12 -0700
From:   Yonghong Song <yhs@...com>
To:     <ast@...com>, <kafai@...com>, <daniel@...earbox.net>,
        <netdev@...r.kernel.org>
CC:     <kernel-team@...com>
Subject: [PATCH bpf-next 0/3] bpf: implement percpu map pretty print for bpffs and bpftool

Commit a26ca7c982cb ("bpf: btf: Add pretty print support to the
basic arraymap") and Commit 699c86d6ec21 ("bpf: btf: add pretty print
for hash/lru_hash maps") added bpffs pretty print for array, hash and
lru hash maps. The pretty print gives users a structurally formatted
dump for keys/values which much easy to understand than raw bytes.

This patch set implemented bpffs pretty print support for
percpu arraymap, percpu hashmap and percpu lru hashmap.
For complex key/value types, the pretty print here is even more useful
due to
  . large volumne of data making it even harder to correlate bytes
    to a particular field in a particular cpu.
  . kernel rounds the value size for each cpu to multiple of 8.
    User has to be aware of this otherwise wrong value may be
    derived from cpu 1/2/...

For example, we may have a bpffs pretty print like below:
   43602: {
        cpu0: {43602,0,-43602,0x3,0xaa52,0x3,{43602|[82,170,0,0,0,0,0,0]},ENUM_TWO}
        cpu1: {43602,0,-43602,0x3,0xaa52,0x3,{43602|[82,170,0,0,0,0,0,0]},ENUM_TWO}
        cpu2: {43602,0,-43602,0x3,0xaa52,0x3,{43602|[82,170,0,0,0,0,0,0]},ENUM_TWO}
        cpu3: {43602,0,-43602,0x3,0xaa52,0x3,{43602|[82,170,0,0,0,0,0,0]},ENUM_TWO}
   }
for a percpu map.

This patch also added percpu formatted print on bpftool. For example,
bpftool may print like below:
    {
        "key": 0,
        "values": [{
                "cpu": 0,
                "value": {
                    "ui32": 0,
                    "ui16": 0,
                }
            },{
                "cpu": 1,
                "value": {
                    "ui32": 1,
                    "ui16": 0,
                }
            },{
                "cpu": 2,
                "value": {
                    "ui32": 2,
                    "ui16": 0,
                }
            },{
                "cpu": 3,
                "value": {
                    "ui32": 3,
                    "ui16": 0,
                }
            }
        ]
    }

Patch #1 implemented bpffs pretty print for percpu arraymap/hash/lru_hash
in kernel. Patch #2 added the test case in tools bpf selftest test_btf.
Patch #3 added percpu map btf based dump.

Yonghong Song (3):
  bpf: add bpffs pretty print for percpu arraymap/hash/lru_hash
  tools/bpf: add bpffs percpu map pretty print tests in test_btf
  tools/bpf: bpftool: add btf percpu map formated dump

 kernel/bpf/arraymap.c                  |  24 +++++
 kernel/bpf/hashtab.c                   |  31 ++++++
 tools/bpf/bpftool/map.c                |  33 +++++-
 tools/testing/selftests/bpf/test_btf.c | 179 ++++++++++++++++++++++++++-------
 4 files changed, 230 insertions(+), 37 deletions(-)

-- 
2.14.3