On 2015/10/17 18:48, Wang Nan wrote:
bpf__config_obj() is introduced as a core API to config BPF object
after loading. One configuration option of maps is introduced. After
this patch BPF object can accept configuration like:
maps.my_map.value=1234
This patch is more complex than the work it really does because the
consideration of extension. In designing of BPF map configuration,
following things should be considered:
1. Array indics selection: perf should allow user setting different
value to different slots in an array, with syntax like:
maps.my_map.value[0,3-6]=1234;
2. Type of value: integer is not the only valid value type. Perf
event can also be put into a map after commit 35578d7984003097af2b1e3
(bpf: Implement function bpf_perf_event_read() that get the selected
hardware PMU conuter);
3. For hash table, it is possible to use string or other as key;
4. It is possible that map configuration is unable to be setup
during parsing. Perf event is an example.
Therefore, this patch does tie following thing for extension:
1. Instead of update map element during parsing, this patch stores
map config options in 'struct bpf_map_priv'. Following patches
would apply those configs at proper time;
Because of this delay-updating manner, current implementation forbid
setting a map with different configuration.
For example:
# perf record -e
test_bpf.c/maps:channel:value[0...9]=1,maps:channel:value[10...19]=2/ ...
is equal to
# perf record -e test_bpf.c/maps:channel:value[10...19]=2/ ...
because [see follow]
2. Make 'struct bpf_map_priv' extensible so following patches can
add new key and value operations;
3. Use bpf_config_map_funcs array to support more maps configuration.
Signed-off-by: Wang Nan <[email protected]>
Signed-off-by: He Kuang <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Brendan Gregg <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: David Ahern <[email protected]>
Cc: He Kuang <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kaixu Xia <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Zefan Li <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/n/[email protected]
---
[SNIP]
+enum bpf_map_priv_key_type {
+ BPF_MAP_PRIV_KEY_ALL,
+};
+
+enum bpf_map_priv_value_type {
+ BPF_MAP_PRIV_VAL_VALUE,
+};
+
+struct bpf_map_priv {
+ struct {
+ enum bpf_map_priv_key_type type;
+ } key;
+
+ struct {
+ enum bpf_map_priv_value_type type;
+ union {
+ u64 val;
+ };
+ } value;
+};
+
... because this structure holds only one config term.
In next version I'd like to save multiple setting operations in
this structure.
Thank you.
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