cvs commit: src/sys/kern init_main.c kern_descrip.c sys_pipe.c uipc_syscalls.c uipc_usrreq.c vfs_syscalls.c src/sys/sys filedesc.h

Nate Lawson nate at
Thu Jan 15 10:11:55 PST 2004

On Thu, 15 Jan 2004, Dag-Erling [iso-8859-1] Smørgrav wrote:
> Tim Robbins <tjr at> writes:
> > Thanks for committing this. I'm interested, though, what was the reason you
> > changed it to use a single bitmap instead of two levels?
> The increased complexity didn't actually translate into a performance
> improvement.  There was no reason to use two levels instead of one.
> The theoretical advantage is logarithmic rather than linear early
> growth, but in practice it wasn't noticeable.  The cost of the logic
> required to maintain and use the high-level bitmap outweighs the gain
> (which is to save a handful of comparisons against zero in the
> low-level bitmap).

A related question, why wasn't sys/bitstring.h used?


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