MAXPHYS and physical memory (Was: Re: siis/atacam/ata/gmirror
8.0-BETA3 disk performance)
mav at FreeBSD.org
Wed Sep 2 15:47:03 UTC 2009
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
Could you show your panic message?
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