Hi everyone, I am super new to bpf and the open source community in general. Please bear with me asking some basic questions. We are working on a bpf monitoring tool to track the CPU and memory usage for all bpf programs loaded in the system. We were able to get CPU usage per bpf program with the BPF_OBJ_GET_INFO_BY_ID syscall on a bpf prog object. We are trying to do the same on a map object to query for per map memory usage. The information returned from bpf_map_info only contains things like max_entries, key_size, value_size, which can be used to calculate estimated memory allocation size. But we are also interested in knowing how much memory is actually being used by our program. For instance, one of our bpf program uses a map with type hashtable. The hashtable is created with a chunk of pre-allocated memory based on the max_entres, key_size and value size. The pre-allocated size is useful information to know but so is the current number of entries in the hashtable. We used to run into a performance issue where our bpf map's max_entries is set to be too small and we end up totally exhausting the pre-allocated memory. So knowing things like current entry count VS max entry count of a hashtable is useful information for us. With that being said, we have a few questions and hopefully we can get some help from the community. 1) We couldn't find anything in bpf_map_info to give us the current entry count of a hashtable. I read that bpf_map_info returns information about a map object in general. So it makes total sense to not have information of a particular map type. But is there an existing place we can get the per map type information (eg, the current entry count of a hashtable, the number of elements pushed to a stack, etc)? 2) If there isn't an existing place to return map type specific information, would it make sense to extend the structure bpf_map_info with a union at the end and have that union to contain per map type specific information? Thanks, Hao
