Date: Wed, 02 Sep 2009 18:46:46 +0300 From: Alexander Motin <mav@FreeBSD.org> To: Mel Flynn <mel.flynn+fbsd.current@mailing.thruhere.net> Cc: "Derek \(freebsd lists\)" <482254ac@razorfever.net>, freebsd-current@freebsd.org Subject: Re: MAXPHYS and physical memory (Was: Re: siis/atacam/ata/gmirror 8.0-BETA3 disk performance) Message-ID: <4A9E9366.9050601@FreeBSD.org> In-Reply-To: <200909021728.21566.mel.flynn%2Bfbsd.current@mailing.thruhere.net> References: <h7lmvl$ebq$1@FreeBSD.cs.nctu.edu.tw> <4A9E8677.1020208@FreeBSD.org> <200909021728.21566.mel.flynn%2Bfbsd.current@mailing.thruhere.net>
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Mel Flynn wrote: > On Wednesday 02 September 2009 16:51:35 Alexander Motin wrote: > >> For maximum linear I/O performance you may want to build kernel with >> options MAXPHYS=(1024*1024) > > I've found that just doubling the default MAXPHYS already panics-on-boot a > 1.5GB i386 system. Is there any reasonable conversion table for MAXPHYS to > physical memory, since various memory related kernel setups are derived from > or calculated with MAXPHYS? What especially your panic was about? It could be bug in ATA(4) or some other code, that does not handle MAXPHYS correctly. I don't think that you could reach memory limit during simple system boot because of that. I am successfully running my testing Pentium-75 with 64MB RAM with 1MB MAXPHYS. Could you show your panic message? -- Alexander Motin
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