sysdig - an open source system-level exploration and troubleshooting tool. Sysdig captures system calls and other system level events using a linux kernel facility called tracepoints, which means much less overhead than strace.
It then "packetizes" this information, so that you can save it into trace files and filter it, a bit like you would do with tcpdump. This makes it very flexible to explore what processes are doing.
Sysdig is also packed with a set of scripts that make it easier to extract useful information and do troubleshooting.