Using a single sysread() helps you win a probabilistic scheduling game, where you are competing against other programs that are also trying to move a disk head to fetch data. Moving a disk head is expensive, and if you can get your entire read satisfied with minimal intervening moves, you win. If you block during a read() and another program (or set of programs) gets requests queued that cause the head to move, you might lose unless the OS is smart enough to be doing read-ahead caching.

If you're the only person on the box, Benchmark tests are rather suspect, since there's not a lot of competition for the disk head. It would be much more interesting to see how the benchmarks differed if you were to run 20 of them simultaneously.

In reply to Re: Re: Reading entire file into scalar: speed differences? by dws
in thread Reading entire file into scalar: speed differences? by theguvnor

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