buildstats: reduce amount of data stored for system utilization
Pre-processing /proc data during the build considerably reduces the
amount of data written to disk: 176KB instead of 4.7MB for a 20
minuted build. Parsing also becomes faster.
The disk monitor log added another 16KB in that example build. The
overall buildstat was 20MB, so the overhead for monitoring system
utilization is small enough that it can be enabled by default.
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
