Re: zone movable patches comments

[mel@skynet.ie (Mel Gorman)]

On (09/07/07 17:50), Nick Piggin didst pronounce:
> Hi Mel,
> 
> Just had a bit of a look at the zone movable stuff in -mm...

Great.

> Firstly,
> would it be possible to list all the dependant patches in that set, or
> is it just those few that are contiguous in Andrew's series file?
> 

add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated.patch
and the few that are contiguous. I'm beginning to test with the
following series file

add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated.patch
create-the-zone_movable-zone.patch
create-the-zone_movable-zone-fix.patch
create-the-zone_movable-zone-fix-2.patch
allow-huge-page-allocations-to-use-gfp_high_movable.patch
allow-huge-page-allocations-to-use-gfp_high_movable-fix.patch
allow-huge-page-allocations-to-use-gfp_high_movable-fix-2.patch
allow-huge-page-allocations-to-use-gfp_high_movable-fix-3.patch
handle-kernelcore=-generic.patch
handle-kernelcore=-generic-fix.patch

There was a minor reject in
add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated.patch
but otherwise applied smoothly.

> A few comments -- can it be made configurable? I guess there is not
> much overhead if the zone is not populated, but there has been a fair
> bit of work towards taking out unneeded zones.
> 

It could be made configurable as zone_type already has configurable
zones. However, as it is that would always be set on distro kernels for
CONFIG_HUGETLB_PAGE, is there any point? It might make sense for embedded
systems but I've received pushback from Andrew before for trying to introduce
config options that affect the allocator before.

> Also, I don't really like the name kernelcore= to specify mem-sizeof
> movable zone. Could it be renamed and stated in the positive, like
> movable_mem= or reserve_movable_mem=?

It could but it was named this way for a reason. It was more important that
the administrator get the amount of memory for non-movable allocations
correct than movable allocations. If the size of ZONE_MOVABLE is wrong,
the hugepage pool may not be able to grow as large as desired. If the size
of memory usable of non-movable allocations is wrong, it's worse.

> And can that option be written
> up in Documentation?
> 

Documentation/kernel-parameters.txt

> What is the status of these patches? Are they working and pretty well
> ready to be merged for 2.6.23?
> 

I have not encountered problems with them in a long time. I'm re-testing now
using 2.6.22 as a baseline but I believe they are ready for merging to 2.6.23.

Thanks

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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