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Date: Thu, 15 Jan 2004 10:11:53 -0800 (PST)
From: Nate Lawson <nate@root.org>
To: Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?= <des@des.no>
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Subject: Re: 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
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On Thu, 15 Jan 2004, Dag-Erling [iso-8859-1] Sm=F8rgrav wrote:
> Tim Robbins <tjr@freebsd.org> 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?

-Nate