can we enable direct_io flag when issue file system API from MLPerf storage test suite

[gaowayne]

currently, we notice, MLPerf storage still leverage page cache a lot, not stress storage enough. can we support one branch that issue direct IO for all places? I see there are too many file open places.

[LouisDDN]

I don't think it makes sense as the goal is to reproduce a workload not to get maximum throughput out of the storage.