Re: [patch] mm: more likely reclaim MADV_SEQUENTIAL mappings II

[Johannes Weiner <hannes@saeurebad.de>]

Finally got some half-way stable time numbers for this patch.

My approach was to generate background activity by dd'ing my hard-drive
to /dev/null and meanwhile copy a 1G file with memcpy() between two
mmaps and then the same file again with MADV_SEQUENTIAL mmaps.  The
numbers below are averages/standard deviations from 8 copy iterations.

I dropped the caches before each copy and waited for them to become
repopulated by the background dd.

The numbers in brackets are the std dev.

mmotm:
    normal  user: 1.775000s [0.053307] system: 9.620000s [0.135339] total: 98.875000s [0.613956]
   madvise  user: 2.552500s [0.041307] system: 9.442500s [0.075980] total: 73.937500s [0.734170]
mmotm+patch:
    normal  user: 1.850000s [0.013540] system: 9.760000s [0.047081] total: 99.250000s [0.569386]
   madvise  user: 2.547500s [0.014930] system: 8.865000s [0.055000] total: 71.897500s [0.144763]

Well, time-wise not sooo much of an improvement.  But given the
massively decreased LRU-rotation [ http://hannes.saeurebad.de/madvseq/ ]
I'm still looking forward to Kosaki-san's throughput measurements :)

	Hannes

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