read performance

/tests/small_file/low_load
/tests/small_file/high_load
/tests/big_file/low_load
/tests/big_file/high_load

/modules/build_env.sh
    function create_big_file

/default-build_env.conf
    testfile=/tmp/bigfile

/modules/read_perf.sh
    function run_readperf
    function ...

/default-read_perf.conf
    filesize=20
    no_threads=5

/tests/small_file.conf
    filesize=10

/tests/big_file.conf
    filesize=10000
    
/tests/low_load.conf
    no_threads=40
    run_list="run_readperf"

/tests/big_file/high_load/small_buf
/tests/small_buf.conf
    bufsize=4