Re: mm-more-likely-reclaim-madv_sequential-mappings.patch

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> > I have a note here that this patch needs better justification.  But the
> > changelog looks good and there are pretty graphs, so maybe my note is stale.
> > 
> > Can people please check it?
> > 
> > Thanks.
> 
> maybe, I can run benchmark it.
> please wait few hour.

1. mesured various copy performance.
   using copybench -> http://code.google.com/p/copybench/

   my machine mem:   8GB
   target file size: 10GB (filesize > system mem)


                         2.6.27    mmotm-1010:
   ==============================================================
   rw_cp                 6:13      6:11
   rw_fadv_cp            6:09      6:06
   mm_sync_cp            5:51      5:55
   mm_sync_madv_cp       5:59      5:57
   mw_cp                 5:50      5:50
   mw_madv_cp            5:55      5:55


   So, no improvement, but no regression.


2. Latency degression ratio of Sequential copy v.s. Other I/O situation

	run following script (mm_sync_madv_cp is one of copybench program)

	$ dbench -D /disk2/ -c client.txt 100 &
	$ sleep 100
	$ time ./mm_sync_madv_cp src dst


                         2.6.27    mmotm-1010
   ==============================================================
   mm_sync_madv_cp       6:14      6:02         (min:sec)
   dbench throughput     12.1507   14.6273      (MB/s)
   dbench latency        33046     21779        (ms)


   So, throughput improvement is relativily a bit, but latency improvement is much.
   Then, I think the patch can improve "larege file copy (e.g. backup operation)
   attacks desktop latency" problem.

Any comments?


Thanks.


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