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Re: EnableHiMem for Memory == exactly 1GB?



On Tue, Jun 29, 2004 at 11:25:03PM -0700, William Ballard said
> Greg Madden in <[🔎] 200406261122.05053.gomadtroll@gci.net>, suggested 
> enabling CONFIG_HIGHMEM4G=y for machines with > 960MB memory; however 
> the help for this option in 2.6.7 says "if you will never run a machine 
> with more than 1 Gigabyte of memory."
> 
> It seems to suggest that for the interval [0,1024] it should be not set 
> and (1024,4096] it should be set; i.e. not set at exactly 1GB.  Is this 
> correct?

I'm pretty sure the limit is at 896MB of RAM.  Without HIGHMEM, the
kernel will ignore all memory above that.  With it, the kernel will use
up to $bignum GB of RAM, but (some? all? I forget) memory access will be
slower.  The conventional wisdom seems to be that if you have less than
1GB of RAM, then this slowdown negates the benefit of the extra =< 128
MB of RAM you would have access to.  Or so I've heard; my biggest
machine has 512MB of RAM.  It's probably one of those things where you
need to test it yourself to decide whether it's worth it for you or not.

-- 
Words of the day:  CDMA Firewalls quarter AK-47 bullion unclassified War Crimes

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