Date: Thu, 15 Nov 2012 14:07:28 -0700 From: Warner Losh <imp@bsdimp.com> To: Alan Cox <alc@rice.edu> Cc: "Jayachandran C." <jchandra@freebsd.org>, mips@freebsd.org Subject: Re: ZERO_REGION_SIZE Message-ID: <DF2CB7FC-C1ED-4F4C-A39A-60B5E7FC566D@bsdimp.com> In-Reply-To: <50A54CCD.8070409@rice.edu> References: <50A53391.4080909@rice.edu> <CAJ-Vmon-v3K7012ti_L6ao3wQHfQ99Jau1kJ%2BGhumbPjAuSDww@mail.gmail.com> <50A54CCD.8070409@rice.edu>
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On Nov 15, 2012, at 1:13 PM, Alan Cox wrote: > P.S. I would encourage someone with hardware to look into implementing = a > non-iterative ffs*() using (d)clz. The MIPS pmap would benefit from > this. Basically, most pmap_enter() calls are doing an ffs*(). ffs finds the first bit set. clz counts the number of leading zeros and = thus finds the last bit set. Would a non-iterative fls* be helpful? Warner
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