Date: Thu, 03 Sep 2009 00:20:43 +0300 From: Alexander Motin <mav@FreeBSD.org> To: Mel Flynn <mel.flynn+fbsd.current@mailing.thruhere.net> Cc: freebsd-current@freebsd.org Subject: Re: MAXPHYS and physical memory (Was: Re: siis/atacam/ata/gmirror 8.0-BETA3 disk performance) Message-ID: <4A9EE1AB.3040307@FreeBSD.org> In-Reply-To: <200909022301.03825.mel.flynn%2Bfbsd.current@mailing.thruhere.net> References: <h7lmvl$ebq$1@FreeBSD.cs.nctu.edu.tw> <200909021728.21566.mel.flynn%2Bfbsd.current@mailing.thruhere.net> <4A9E9366.9050601@FreeBSD.org> <200909022301.03825.mel.flynn%2Bfbsd.current@mailing.thruhere.net>
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Mel Flynn wrote: > On Wednesday 02 September 2009 17:46:46 Alexander Motin wrote: >> 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? > > It's been a while since I last tried, during 7.1-STABLE. Two different > machines wouldn't boot, both 1.5G; loading kernel.old, then commenting the > MAXPHYS change, rebuilding kernel made things work, so I stopped pursuing this > at the time. > I remember the panic message quite early page fault, one of the first drivers > loaded (ahci or acpi). Since this is supposed to work, I'm going to pursue it > further and see if I can still reproduce it. I have fixed MAXPHYS issue in ata-ahci in RELENG_8, but I haven't merged it lower as code is quite different. So it would be nice if you can check it on 8.x. -- Alexander Motin
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