benchmarking

I am doing a simple scaling test on Spark using sort benchmark -- from 1 core, up to 8 cores. I notice that 8 cores is slower than 1 core. //run spark using 1 core spark-submit --master local[1] --class john.sort sort.jar data_800MB.txt data_800MB_output //run spark using 8 cores spark-submit --master local[8] --class john.sort sort.jar data_800MB.txt data_800MB_output The input and output directories in each case, are in HDFS. 1 core: 80 secs 8 cores: 160 secs I would expect 8 cores performance to have x amount of speedup. user6910411 Theoretical limitations I assume you are familiar Amdahl's

I want to know what is the best way to benchmark my PHP scripts. Does not matter if a cron job, or webpage or web service. I know i can use microtime but is it really giving me the real time of a PHP script? I want to test and benchmark different functions in PHP that do the same thing. For example, preg_match vs strpos or domdocument vs preg_match or preg_replace vs str_replace` Example of a webpage: <?php // login.php $start_time = microtime(TRUE); session_start(); // do all my logic etc... $end_time = microtime(TRUE); echo $end_time - $start_time; This will output: 0.0146126717 (varies all

I am trying to optimize one part of my code that inserts data into MySQL. Should I chain INSERTs to make one huge multiple-row INSERT or are multiple separate INSERTs faster? https://dev.mysql.com/doc/refman/8.0/en/insert-optimization.html The time required for inserting a row is determined by the following factors, where the numbers indicate approximate proportions: Connecting: (3) Sending query to server: (2) Parsing query: (2) Inserting row: (1 × size of row) Inserting indexes: (1 × number of indexes) Closing: (1) From this it should be obvious, that sending one large statement will save