Re: [HACKERS] WAL logging problem in 9.4.3?

At Tue, 10 Dec 2019 16:59:25 +0900 (JST), Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote in
> shared_buffers=1GB/wal_buffers=16MB(defalut). pgbench -s 20 uses 256MB
> of storage so all of them can be loaded on shared memory.
>
> The attached graph shows larger benefit in TPS drop and latency
> increase for HDD. The DDL pages at the corsspoint between commit-FPW
> and commit-sync moves from roughly 300 to 200 in TPS and latency, and
> 1000 to 600 in DDL runtime. If we can rely on the two graphs, 500 (or
> 512) pages seems to be the most promising candidate for the default
> value of wal_skip_threshold.
> regards.

I rebased the patch and changed the default value for the GUC variable
wal_skip_threshold to 4096 kilobytes in config.sgml, storage.c and
guc.c. 4096kB is choosed as it is the nice round number of 500 pages *
8kB = 4000kB.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center