Re: [Testperf-general] BufferSync and bgwriter

On Mon, 2004-12-13 at 04:39, Mark Kirkwood wrote:
> I am seeing a reasonably reproducible performance boost after applying
> your patch (I'm not sure if that was one of the main objectives, but it
> certainly is nice).
>
> I *was* seeing a noticeable decrease between 7.4.6 and 8.0.0RC1 running
> pgbench. However, after applying your patch, 8.0 is pretty much back to
> being the same.
>

Thanks Mark - brilliant to have some confirming test results back so
quickly.

The tests indicate that we're on the right track here and that we should
test this on the OSDL platform also on a long run, to check out the
effects of both normal running and checkpointing.

Given these test settings:
bgwriter_delay = 200
bgwriter_percent = 2
bgwriter_maxpages = 100

This shows the importance of reducing the length of the BufMgr lock in
StrategyDirtyBufferList() -- which I think Neil also agrees is the main
problem here.
>
> ______________________________________________________________________
> System
> ------
> P4 2.8Ghz 1G 1xSeagate Barracuda 40G
> Linux 2.6.9 glibc 2.3.3 gcc 3.4.2
> Postgresql 7.4.6 | 8.0.0RC1
>
> Test
> ----
> Pgbench with scale factor = 200
>
> Pg 7.4.6
> --------
>
> clients transactions tps
> 1 1000 65.1
> 2 1000 72.5
> 4 1000 69.2
> 8 1000 48.3
>
>
> Pg 8.0.0RC1
> -----------
>
> clients transactions tps tps (new buff patch + settings)
> 1 1000 55.8 70.9
> 2 1000 68.3 77.9
> 4 1000 38.4 62.8
> 8 1000 29.4 38.1
>
> (averages over 3 runs, database dropped and recreated after each set, with a
> checkpoint performed after each individual run)
>
>
> Parameters
> ----------
>
> Non default postgresql.conf parameters:
>
> tcpip_socket = true [listen_addresses = "*"]
> max_connections = 100
> shared_buffers = 10000
> wal_buffers = 1024
> checkpoint_segments = 10
> effective_cache_size = 40000
> random_page_cost = 0.8
>
> bgwriter settings (used with patch only)
>
> bgwriter_delay = 200
> bgwriter_percent = 2
> bgwriter_maxpages = 100
--
Best Regards, Simon Riggs