Messages in this thread | | | Date | Thu, 2 Jul 2009 10:42:27 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: adjusting lowmem_reserve_ratio on an embedded system? |
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On Wed, 1 Jul 2009 14:23:52 +0200 Daniel Kabs <daniel.kabs@gmx.de> wrote:
> Hello, > > in tracing a low on memory situation on an embedded system I came across > the Documentation/sysctl/vm.txt. There it is advised to change the > lowmem_reserve_ratio on systems running without swap. > > I wonder if this applies for an embedded system running with 256MByte RAM > and no swap which is using only one memory zone (ZONE_NORMAL)? I guess > no. > > > To understand what the parameter means I read the relevant section from > vm.txt and came across the terms "lowmem zone" and "lower zones" > and "lowmem memory". I feel dumb. I could not find a concept of "lower > zones" (or "upper" zones). What exactly do they mean? > Assume a system with HIGHMEM/NORMAL/DMA
zone fallback list is created as
HIGHMEM->NORMAL->DMA
HIGHMEM's lower zone is NORMAL+DMA NORMAL's lower zone is DMA.
"lowmem" often means NORMAL+DMA (yes, there are HIGHMEM) but it depends on context.
Regards, -Kame
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