Reading from stdin significantly slower than reading file directly?

[methonash]

Thank you all very much for your detailed feedback!

I wound up pulling the "TREE_GRM_ESTN.csv" file referred to by 
Jon and used it in subsequent tests. Created D-programs for 
reading directly through a File() structure, versus reading 
byLine() from the stdin alias.

After copying the large CSV file to /dev/shm/ (e.g. a ramdisk), I 
re-ran the two programs repeatedly, and I was able to approach 
the 20-30% overhead margin I would expect to see for using a 
shell pipe and its buffer; my results now similarly match Jon's 
above.

Lesson learned: be wary of networked I/O systems (e.g. Isilon 
storage arrays); all kinds of weirdness can happen there ...