Date: Thu, 21 Sep 2006 17:46:59 +0300 From: Danny Braniss <danny@cs.huji.ac.il> To: freebsd-hackers@FreeBSD.ORG Subject: Re: numbers don't lie ... Message-ID: <E1GQPpL-000IWx-R9@cs1.cs.huji.ac.il> In-Reply-To: <200609210831.k8L8VxvK007258@lurza.secnetix.de> References: <200609210831.k8L8VxvK007258@lurza.secnetix.de>
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[...] > But when you perform the buildworld several times (as you > should do when you're benchmarking properly), everything > is already in the RAM disk. If you instead rely on caching > but you don't have enough RAM to hold all of src + obj + > toolchain in RAM, then src (or at least parts of it) will > have to be read from the physical disk again upon each > buildworld. > > By the way, the contents of the RAM disk are _not_ cached > in RAM, so they don't waste RAM twice. That was only a > problem with the old vn(4)/vnconfig(8) in FreeBSD 4. > > Best regards > Oliver you might have a point, but this started when I asked why, two boxes, under similar test gave idential real times, but very different user times. dell-2950 : make -j8 TARGET_ARCH=amd64 buildworld: 24m8.28s real 1h2m59.38s user 16m16.20s sys sunfire : make -j8 TARGET_ARCH=amd64 buildworld: 23m47.69s real 48m53.58s user 13m44.81s sys and SUN X4100: Dual Core AMD Opteron(tm) Processor 280 (2393.19-MHz K8-class CPU) one 70g sas disk (via mpt) -- x 2 DELL 2950: Intel(R) Xeon(TM) CPU 3.20GHz (3192.98-MHz K8-class CPU) 4 sata disks + raid0 (via mfi) -- dual core x 2 cheers, danny
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