Re: [PATCH] mm/compaction: reset compaction scanner positions

[David Rientjes <rientjes@google.com>]

On Sat, 21 Mar 2015, Gioh Kim wrote:

> When the compaction is activated via /proc/sys/vm/compact_memory
> it would better scan the whole zone.
> And some platform, for instance ARM, has the start_pfn of a zone is zero.
> Therefore the first try to compaction via /proc doesn't work.
> It needs to force to reset compaction scanner position at first.
> 
> Signed-off-by: Gioh Kim <gioh.kim@lge.c>

That shouldn't be a valid email address.

> Acked-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: David Rientjes <rientjes@google.com>

I was thinking that maybe this would be better handled as part of the 
comapct_zone() logic, i.e. set cc->free_pfn and cc->migrate_pfn based on a 
helper function that understands cc->order == -1 should compact the entire 
zone.  However, after scanning the entire zone as a result of this write, 
the existing cached pfns probably don't matter anymore.  So this seems 
fine.

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