Date: Mon, 05 May 2003 13:12:17 -0500 From: Eric Anderson <anderson@centtech.com> To: Kyle Rollin <knr@xy.hartford.edu> Cc: freebsd-performance@freebsd.org Subject: Re: Real and availible RAM Message-ID: <3EB6A981.1030504@centtech.com> References: <3801.172.182.185.39.1052141430.squirrel@bluhayz.homeunix.org> <20030505180224.M13866@xy.hartford.edu>
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Kyle Rollin wrote: > On Mon, 5 May 2003 09:30:30 -0400 (EDT), agent dero wrote > >>I have been looking through the kernel boot messages in /var/log >>while working on some custom kernel compile work, and I came across > > something > >>that I think is very interesting, but doesn't make sense. >>real memory = 100663296 (98304K bytes) >>avail memory = 94580736 (92364K bytes) >> >>This tells me that FreeBSD recognizes my 98MB of RAM, but it only >>uses 92MB? Are the 6MB of RAM that are left getting shafted, and >>just using power, but not being addressed by FreeBSD? Does this slow >>down my machine at all, I mean, is there a percentage to this? Where >>only x% of 100% RAM is availible or usable? >> > > > <snip> > > If you look at the way x86 architecture is designed (and somebody else can > feel free to correct me if I'm wrong), but system memory is often used in > the caching/shadowing of BIOS. This is where a lot of system memory often > goes before the OS is loaded - also, as Rob said, the kernel itself will > take up memory before the rest of the OS is booted. I believe that the BIOS steals the ram prior to the OS booting, so that the box does not show that as part of the total ram.. Like: CPU: VIA/IDT Unknown (1066.16-MHz 686-class CPU) Origin = "CentaurHauls" Id = 0x693 Stepping = 3 Features=0x380b13d<FPU,DE,PSE,TSC,MSR,CX8,MTRR,PGE,CMOV,MMX,FXSR,SSE> real memory = 234815488 (223 MB) avail memory = 221167616 (210 MB) Eric -- ------------------------------------------------------------------ Eric Anderson Systems Administrator Centaur Technology Attitudes are contagious, is yours worth catching? ------------------------------------------------------------------
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