Date: Sun, 21 Mar 1999 17:15:00 +0000 (GMT) From: Andy Doran <ad@psn.ie> To: zhihuizhang <bf20761@binghamton.edu> Cc: Luigi Rizzo <luigi@labinfo.iet.unipi.it>, freebsd-hackers@FreeBSD.ORG Subject: Re: Calculation of load average and CCPU_SHIFT Message-ID: <Pine.BSF.4.05.9903211711550.288-100000@vmunix.psn.ie> In-Reply-To: <Pine.SOL.L3.93.990321120025.21143A-100000@bingsun2>
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> I have never heard of this. Can you explain a little bit more on why FPU > usage is not allowed in the kernel or give me pointers where I can find > more information on this topic? If you use FP code in the kernel that means that you then have to save the FPU context (registers etc.) and reload then again when you return from a syscall, or switch to another process. This is costly. Also, there's no guarentee that the machine has an FPU, so using fixed-point is basically the only way to go, since the emulation overhead is gross. Andy. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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