ftrace: Store and retrieve window params in trace cache
ftrace: Store and retrieve window params in trace cache

Store a JSON file with the parameters used to parse a trace in the cache. If, on
retrieval, we find a mismatch then simply invalidate the cache.

A richer implementation might detect whether we can still use the cache (e.g. if
the requested window is a subset of the cached one), but for now I don't think
that's worth the effort/complexity.

Reviewed-by: KP Singh <d2841bc036e0f1e3090bf6691da4b34cb2d724be@google.com>

bjackman/trappy,ARM-software/trappy,ARM-software/trappy,bjackman/trappy,bjackman/trappy,ARM-software/trappy,bjackman/trappy,ARM-software/trappy