Re: Avoiding external fragmentation with a placement policy Version 12

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

Mike Kravetz wrote:
> On Thu, Jun 02, 2005 at 09:09:23AM +1000, Nick Piggin wrote:
> 
>>It adds a lot of complexity to the page allocator and while
>>it might be very good, the only improvement we've been shown
>>yet is allocating lots of MAX_ORDER allocations I think? (ie.
>>not very useful)
>>
> 
> 
> Allocating lots of MAX_ORDER blocks can be very useful for things
> like hot-pluggable memory.  I know that this may not be of interest
> to most.  However, I've been combining Mel's defragmenting patch
> with the memory hotplug patch set.  As a result, I've been able to
> go from 5GB down to 544MB of memory on my ppc64 system via offline
> operations.  Note that ppc64 only employs a single (DMA) zone.  So,
> page 'grouping' based on use is coming mainly from Mel's patch.
> 

Back in the day, Linus would tell you to take a hike if you
wanted to complicate the buddy allocator to better support
memory hotplug ;)

I don't know what's happened to him now though, he seems to
have gone a little soft on you enterprise types.

Seriously - thanks for the data point, I had an idea that you
guys wanted this for mem hotplug.

-- 
SUSE Labs, Novell Inc.

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