Messages in this thread | | | Date | Thu, 28 Jun 2012 09:55:46 +0900 | From | Minchan Kim <> | Subject | Re: excessive CPU utilization by isolate_freepages? |
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On 06/28/2012 09:28 AM, Rik van Riel wrote:
> On 06/27/2012 07:59 PM, Minchan Kim wrote: > >> I doubt compaction try to migrate continuously although we have no >> free memory. >> Could you apply this patch and retest? >> >> https://lkml.org/lkml/2012/6/21/30 > > Another possibility is that compaction is succeeding every time, > but since we always start scanning all the way at the beginning > and end of each zone, we waste a lot of CPU time rescanning the > same pages (that we just filled up with moved pages) to see if > any are free.
It does make sense.
> > In short, due to the way compaction behaves right now, > compaction + isolate_freepages are essentially quadratic. > > What we need to do is remember where we left off after a > successful compaction, so we can continue the search there > at the next invocation. >
Good idea. It could enhance parallel compaction, too. Of course, if we can't meet the goal, we need loop around from start/end of zone.
-- Kind regards, Minchan Kim
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