Re: [PATCH] mm: limit lowmem_reserve

[Nick Piggin <nickpiggin@yahoo.com.au>]

Con Kolivas wrote:
> On Saturday 08 April 2006 10:55, Nick Piggin wrote:
> 
>>Con Kolivas wrote:
>>
>>>On Friday 07 April 2006 22:40, Nick Piggin wrote:
>>>
>>>>How would zone_watermark_ok always fail though?
>>>
>>>Withdrew this patch a while back; ignore
>>
>>Well, whether or not that particular patch isa good idea, it
>>is definitely a bug if zone_watermark_ok could ever always
>>fail due to lowmem reserve and we should fix it.
> 
> 
> Ok. I think I presented enough information for why I thought zone_watermark_ok 
> would fail (for ZONE_DMA). With 16MB ZONE_DMA and a vmsplit of 3GB we have a 
> lowmem_reserve of 12MB. It's pretty hard to keep that much ZONE_DMA free, I 
> don't think I've ever seen that much free on my ZONE_DMA on an ordinary 
> desktop without any particular ZONE_DMA users. Changing the tunable can make 
> the lowmem_reserve larger than ZONE_DMA is on any vmsplit too as far as I 
> understand the ratio.
> 

Umm, for ZONE_DMA allocations, ZONE_DMA isn't a lower zone. So that
12MB protection should never come into it (unless it is buggy?).

-- 
SUSE Labs, Novell Inc.
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