Ping... Can someone please help to shed some light on this? Thanks, Hao On Sun, Jul 3, 2022 at 3:33 PM Hao Xiang . <hao.xiang@xxxxxxxxxxxxx> wrote: > > 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
