Messages in this thread | | | Date | Thu, 21 Jan 2010 10:11:12 +0000 | From | Mel Gorman <> | Subject | Re: [RFC-PATCH 0/7] Memory Compaction v1 |
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On Thu, Jan 21, 2010 at 12:12:11PM +0900, KOSAKI Motohiro wrote: > Hi Mel, > > Sorry, I haven't read this patch at all. > > > The time differences are marginal but bear in mind that this is an ideal > > case of mostly unmapped buffer pages. On nice set of results is between > > allocations 13-18 where no pages were reclaimed, some compaction occured > > and 300 huge pages were allocated in 0.16 seconds. Furthermore, compaction > > allocated a high higher percentage of memory (91% of RAM as huge pages). > > > > The downside appears to be that the compaction kernel reclaimed even more > > pages than the vanilla kernel. However, take the cut-off point of 880 pages > > that both kernels succeeded. The vanilla kernel had reclaimed 105132 pages > > at that point. The kernel with compaction had reclaimed 59071, less than > > half of what the vanilla kernel reclaimed. i.e. the bulk of pages reclaimed > > with the compaction kernel were to get from 87% of memory allocated to 91% > > as huge pages. > > > > These results would appear to be an encouraging enough start. > > > > Comments? > > I think "Total pages reclaimed" increasing is not good thing ;)
First, I made a mistake in the patch. With the bug fixed, they're reduced. See the post later in the thread http://lkml.org/lkml/2010/1/6/215
> Honestly, I haven't understand why your patch increase reclaimed and > the exactly meaning of the your tool's rclm field. > > Can you share your mesurement script? May I run the same test? >
Unfortunately at the moment it's part of a mini-testgrid setup I run out of the house. It doesn't lend itself to being stand-alone. I'll break it out as part of the next release.
> I like this patch, but I don't like increasing reclaim. I'd like to know > this patch require any vmscan change and/or its change mitigate the issue. >
With the bug repaired, reclaims go from 105132 to 45935 with more huge pages allocated so right now, no special action is required.
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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