> > I've got a P90 laptop with 40M *1. Somewhere between 2.3.24 and
> > 2.3.27-final the kernel started keeping 15M or more free all the time.
> > On a 40M laptop that makes a big difference. *smile*
>
> 2.3.27 seperates DMA memory from the rest but forgets that you need to
> pull from the DMA pool for a failing GFP_KERNEL allocation.
well, we automatically fall back to lower level zones, check out
__get_pages():
do {
page = rmqueue(zone, order);
if (page)
return page;
} while (zone-- != zones) ;
So we are falling back from ZONE_HIGHMEM to ZONE_NORMAL to ZONE_DMA.
> You also need to figure very fast when you will need to do this otherwise
> your performance goes through the floor.
it should be rather fast. But if higher-order zones are completely
allocated then we are under heavy memory pressure anyway. But it should
work already.
-- mingo
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