Message-ID: <43D0BE27.5000807@jp.fujitsu.com>
Date: Fri, 20 Jan 2006 19:40:39 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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To: Mel Gorman <mel@csn.ul.ie>
CC: Joel Schopp <jschopp@austin.ibm.com>, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org, lhms-devel@lists.sourceforge.net
Subject: Re: [Lhms-devel] Re: [PATCH 0/5] Reducing fragmentation using zones
References: <20060119190846.16909.14133.sendpatchset@skynet.csn.ul.ie> <43CFE77B.3090708@austin.ibm.com> <43D02B3E.5030603@jp.fujitsu.com> <Pine.LNX.4.58.0601200102040.15823@skynet> <43D03C24.5080409@jp.fujitsu.com> <Pine.LNX.4.58.0601200934300.10920@skynet>
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Mel Gorman wrote:>
> What sort of tests would you suggest? 
> The tests I have been running to date are
> 
> "kbuild + aim9" for regression testing
> 
> "updatedb + 7 -j1 kernel compiles + highorder allocation" for seeing how
> easy it was to reclaim contiguous blocks
> 
> What tests could be run that would be representative of real-world
> workloads?
> 

1. Using 1000+ processes(threads) at once
2. heavy network load.
3. running NFS
is maybe good.

>>>> And, for people who want to remove range of memory, list-based approach
>>>> will
>>>> need some other hook and its flexibility is of no use.
>>>> (If list-based approach goes, I or someone will do.)
>>>>
>>> Will do what?
>>>
>> add kernelcore= boot option and so on :)
>> As you say, "In an ideal world, we would have both".
>>
> 
> List-based was frowned at for adding complexity to the main path so we may
> not get list-based built on top of zone based even though it is certinatly
> possible. One reason to do zone-based was to do a comparison between them
> in terms of complexity. Hopefully, Nick Piggin (as the first big objector
> to the list-based approach) will make some sort of comment on what he
> thinks of zone-based in comparison to list-based.
> 
I think there is another point.

what I concern about is Linus's word ,this:
> My point is that regardless of what you _want_, defragmentation is 
> _useless_. It's useless simply because for big areas it is so expensive as 
> to be impractical.

You should make your own answer for this before posting.

 From the old threads (very long!), I think  one of the point was :
To use hugepages, sysadmin can specifies what he wants at boot time.
This guarantees 100% allocation of needed huge pages.
Why memhotplug cannot specifies "how much they can remove" before booting.
This will guaranntee 100% memory hotremove.

I think hugetlb and memory hotplug cannot be good reason for defragment.

Finding the reason for defragment is good.
Unfortunately, I don't know the cases of memory allocation failure
because of fragmentation with recent kernel.

-- Kame


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