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