Re: [PATCH v3 3/3] samples/bpf: example of get selected PMU counter value

xiakaixu
2015-07-24T01:54:25Z

于 2015/7/24 6:59, Alexei Starovoitov 写道:
> On 7/23/15 2:42 AM, Kaixu Xia wrote:
>> This is a simple example and shows how to use the new ability
>> to get the selected Hardware PMU counter value.
>>
>> Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
> ...
>> +struct bpf_map_def SEC("maps") my_map = {
>> + .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
>> + .key_size = sizeof(int),
>> + .value_size = sizeof(unsigned long),
>> + .max_entries = 32,
>> +};
>
> wait. how did it work here? value_size should be u32.

I tested the whole thing on ARM board. You are ringt, it
should be u32.
When create the array map, we choose the array->elem_size as
round_up(attr->value_size, 8), why 8?

Thanks!
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