title: Functionality of the BPF hash of maps structure
body: <p>I'm writing a BPF tool that maintains a per-process trace, which means I'll need a 2d data structure of some sort. To bypass the 512 byte limitation, I've decided that going with the supported structs (maps) is my best bet. After glancing at the <a href="https://github.com/iovisor/bcc/blob/master/docs/reference_guide.md#14-bpf_hash_of_maps" rel="nofollow noreferrer">iovisor docs</a>, it seemed like <code>BPF_HASH_OF_MAPS</code> was the structure I needed. I presumed this structure offered a key-value pairing wherein the "value" was another BPF map. However, based on the parameters it takes, the "outer" structure seems to be an array (personally, from the github documenation, I can't tell the difference between <code>BPF_HASH_OF_MAPS</code> and <code>BPF_ARRAY_OF_MAPS</code>). Have I been misled: does the <code>BPF_HASH_OF_MAPS</code> structure provide hashmap like functionality?</p>