[antlr-interest] Re: Java memory mapped IO is slow for big files :(
Terence Parr
parrt at cs.usfca.edu
Wed Nov 17 16:01:57 PST 2004
On Nov 17, 2004, at 2:22 PM, lgcraymer wrote:
> Ter--
>
> Given the normal variations in timing, it looks like memory-mapped I/O
> and char[file] are almost identical.
Almost...mmap has a slight advantage; I can crank up n very large and
still see it (for small files).
> That is reasonable--they should
> be pretty close, and the figures look right: for the large file,
> reading the entire file will be slightly faster than paging the
> mmapped file, but for the large file, mmap will page in 4K while the
> char[size-of-file] will do two separate accesses.
What do mean by two accesses?
> What do you bet
> that the difference between those and the buffered read() is bounds
> checking?
both have to check an array though right?
Ter
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