Test was done on VM with 4X CPU E5-2660 2.20GHz + 4GB mem with tools written by pgbench-tools on postgresql 9.4.5

settings: run test 3 times by 10 min, db size 100(1.5gb) 400(6gb) 700 (10gb) 1000 (15gb), clients 1,2,4,8,16,32

Results: with the exception of an anomalous drawdown in the last test, without selinux performance gain can reaches 20%

raw data:
pg_selinux_res

select * from (select set,dbsize,clients,avg(tps) avg_tps, round (100*(  1-lag ( avg(tps)) over ( order by dbsize,clients,set)/avg(tps)),1)  diff_pct,scale from v1 group by set,dbsize,scale,clients order by  dbsize,clients,set) t where t.set =4 order by scale,clients;
 set | dbsize  | clients |        avg_tps         | diff_pct | scale
-----+---------+---------+------------------------+----------+-------
   4 | 1502 MB |       1 |  7002.7727490000000000 |      2.1 |   100
   4 | 1502 MB |       2 |     13726.746474333333 |      0.8 |   100
   4 | 1502 MB |       4 |     24392.296147000000 |      2.6 |   100
   4 | 1502 MB |       8 |     24276.725237333333 |      2.3 |   100
   4 | 1502 MB |      16 |     23974.144015000000 |      0.2 |   100
   4 | 1502 MB |      32 |     25629.092840000000 |      0.5 |   100
   4 | 5988 MB |       1 |  2633.2450016666666667 |      4.2 |   400
   4 | 5988 MB |       2 |  4668.1277356666666667 |     15.8 |   400
   4 | 5988 MB |       4 |  7622.5932590000000000 |     14.1 |   400
   4 | 5988 MB |       8 |  9906.9333880000000000 |      8.7 |   400
   4 | 5988 MB |      16 | 12596.0858780000000000 |     20.4 |   400
   4 | 5988 MB |      32 | 13229.7484046666666667 |     18.1 |   400
   4 | 10 GB   |       1 |  2073.9020166666666667 |      1.8 |   700
   4 | 10 GB   |       2 |  3829.0723596666666667 |      7.8 |   700
   4 | 10 GB   |       4 |  6281.3118036666666667 |      7.2 |   700
   4 | 10 GB   |       8 |  8431.4767026666666667 |      8.0 |   700
   4 | 10 GB   |      16 | 11576.7615346666666667 |     19.2 |   700
   4 | 10 GB   |      32 | 13192.6005800000000000 |     20.4 |   700
   4 | 15 GB   |       1 |  1586.9348243333333333 |     -9.0 |  1000
   4 | 15 GB   |       2 |  3034.7334050000000000 |     -2.6 |  1000
   4 | 15 GB   |       4 |  5172.9388216666666667 |     -7.6 |  1000
   4 | 15 GB   |       8 |  7585.5694350000000000 |     -0.7 |  1000
   4 | 15 GB   |      16 | 10037.6583543333333333 |      5.3 |  1000
   4 | 15 GB   |      32 | 11943.1506076666666667 |     16.1 |  1000

So, for better results selinux should be disabled