Re: [patch part 2] Re: [patch] Re: PostgreSQL pgbench performance regression in 2.6.23+

[Mike Galbraith <efault@gmx.de>]

On Sat, 2008-06-07 at 19:53 +0200, Mike Galbraith wrote:
> On Sat, 2008-06-07 at 18:12 +0200, Peter Zijlstra wrote:

> > Just wondering, how much effect does the last_preempter stuff have?, it
> > seems to me the minimum runtime check ought to throttle these wakeups
> > quite a bit as well.
> 
> Without last_preempter, you'd have all tasks having a minimum runtime.
> That would harm the single cpu starve.c testcase for sure, and anything
> like it.  I wanted to target this pretty accurately to 1:N type loads.
> 
> If you mean no trying to disperse preempters, I can test without it.

pgbench
    2.6.26-rc5+                    2.6.26-rc5+ with no disperse
1  10165.511814    10183.705908    10191.865953    10186.995546
2  14994.697875    15204.900479    15209.856474    15239.639522
3  16554.371722    17279.376443    16431.588533    15828.812843
4  18447.345925    18088.861169    15967.533533    16827.107528
5  20119.250823    18537.351094    17890.057368    18829.423686
6  21439.841579    22634.887824    18562.389387    18907.807327
8  25579.379337    25908.373483    19527.104304    19687.221241
10 23876.035623    22403.867804    22635.429472    20627.666899
15 23276.797649    23595.597093    22695.938882    22233.399329
20 23603.315133    23256.506240    22623.205980    22637.340746
30 23633.448266    23229.286697    22736.523283    22691.638135
40 22925.552706    23081.526954    20037.610595    22174.404351
50 19102.481374    19558.624434    21459.370223    21664.820102