What is the fastest way to read 10 GB file from the disk?

Question

We need to read and count different types of messages/run some statistics on a 10 GB text file, e.g a FIX engine log. We use Linux, 32-bit, 4 CPUs, Intel, coding in Perl but the

Answer 1

Most of the time you will be I/O bound not CPU bound, thus just read this file through normal Perl I/O and process it in single thread. Unless you prove that you can do more I/O than your single CPU work, don't waste your time with anything more. Anyway, you should ask: Why on Earth is this in one huge file? Why on Earth don't they split it in a reasonable way when they generate it? It would be magnitude more worth work. Then you can put it in separate I/O channels and use more CPU's (if you don't use some sort of RAID 0 or NAS or ...).

Measure, don't assume. Don't forget to flush caches before each test. Remember that serialized I/O is a magnitude faster than random.