Re: patch to allow disable of WAL recycling

On 07/10/2018 01:15 PM, Jerry Jelinek wrote:
> Thanks to everyone who took the time to look at the patch and send me 
> feedback.  I'm happy to work on improving the documentation of this 
> new tunable to clarify when it should be used and the implications. 
> I'm trying to understand more specifically what else needs to be done 
> next. To summarize, I think the following general concerns were 
> brought up.
>
> For #6, there is no feasible way for us to recreate our workload on 
> other operating systems or filesystems. Can anyone expand on what 
> performance data is needed?
>

I think a simple way to prove this would be to run BenchmarkSQL against 
PostgreSQL in a default configuration with pg_xlog/pg_wal on a 
filesystem that is COW (zfs) and then run another test where 
pg_xlog/pg_wal is patched with your patch and new behavior and then run 
the test again. BenchmarkSQL is a more thorough benchmarking tool that 
something like pg_bench and is very easy to setup.

The reason you would use a default configuration is because it will 
cause a huge amount of wal churn, although a test with a proper wal 
configuration would also be good.

Thanks,

JD



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