Date: Thu, 15 Jan 2004 12:40:34 +0100 From: des@des.no (Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?=) To: Tim Robbins <tjr@freebsd.org> Cc: cvs-all@FreeBSD.org 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 Message-ID: <xzpwu7tignh.fsf@dwp.des.no> In-Reply-To: <20040115111219.GA20914@cat.robbins.dropbear.id.au> (Tim Robbins's message of "Thu, 15 Jan 2004 22:12:19 %2B1100") References: <200401151015.i0FAF49u009868@repoman.freebsd.org> <20040115111219.GA20914@cat.robbins.dropbear.id.au>
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Tim Robbins <tjr@freebsd.org> writes: > Thanks for committing this. I'm interested, though, what was the reason y= ou > 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). DES --=20 Dag-Erling Sm=F8rgrav - des@des.no
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