Re: [Lhms-devel] Re: [PATCH 0/5] Reducing fragmentation using zones

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

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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