Re: WIP patch for latestCompletedXid method of computing snapshot xmax

Hello Tom,

Tom Lane wrote:
> So on the strength of that, I'm going to go ahead and commit the patch,
> but I'd be interested to see benchmarks from people with access to
> better hardware.

I've just completed two dbt2 test runs on a mid-level system, with 4GB 
RAM and a 7 disk SATA RAID 1+0 w/ BBU. Once with code as of 2007/09/05 
18:00 (which is *before* the first lazy xid commit) and once with cvs 
HEAD (2007/09/08  +latestCompletedXid.patch.

Here are the results from the first test run (test run 33, without lazy 
xid):

> $ cat 33/driver/results.out 
>                          Response Time (s)
>  Transaction      %    Average :    90th %        Total        Rollbacks      %
> ------------  -----  ---------------------  -----------  ---------------  -----
>     Delivery   3.97      3.745 :     7.844        11844                0   0.00
>    New Order  45.35      3.844 :     7.692       135192             1352   1.01
> Order Status   3.95      2.728 :     6.371        11764                0   0.00
>      Payment  42.74      2.649 :     6.349       127415                0   0.00
>  Stock Level   4.00      2.172 :     5.634        11915                0   0.00
> ------------  -----  ---------------------  -----------  ---------------  -----
> 
> 1103.45 new-order transactions per minute (NOTPM)
> 120.1 minute duration
> 0 total unknown errors
> 1003 second(s) ramping up

And that's with HEAD +latestCompletedXid.patch (test run 34):

> $ cat 34/driver/results.out 
>                          Response Time (s)
>  Transaction      %    Average :    90th %        Total        Rollbacks      %
> ------------  -----  ---------------------  -----------  ---------------  -----
>     Delivery   3.96      3.843 :     8.223        11760                0   0.00
>    New Order  45.28      4.049 :     8.451       134398             1300   0.98
> Order Status   3.97      2.877 :     6.815        11777                0   0.00
>      Payment  42.80      2.745 :     6.718       127027                0   0.00
>  Stock Level   4.00      2.280 :     6.129        11859                0   0.00
> ------------  -----  ---------------------  -----------  ---------------  -----
> 
> 1097.71 new-order transactions per minute (NOTPM)
> 120.1 minute duration
> 0 total unknown errors
> 1003 second(s) ramping up

Both tests ran for two hours, had 100 warehouses and 50 connections. 
shared_buffers were set to 1024MB, effective_cachesize = 3800MB, all 
other settings were standard.

Regards

Markus