Re: 答复：[HACKERS] 答复：[HACKERS] about fsync inCLOG buffer write

Hi,

On 2015-09-08 15:58:26 +0800, 周正中(德歌) wrote:
> postgres@digoal-> cat 7.sql
> select txid_current();
>
> postgres@digoal-> pgbench -M prepared -n -r -P 1 -f ./7.sql -c 1 -j 1 -T 100000
> About 32K tps.
> progress: 240.0 s, 31164.4 tps, lat 0.031 ms stddev 0.183
> progress: 241.0 s, 33243.3 tps, lat 0.029 ms stddev 0.127

So you're benchmarking how fast you can assign txids. Is that actually
something meaningful? If you have other writes interleaved you'll write
much more WAL, so there'll be checkpoints and such.

FWIW, if you measure something realistic and there's checkpoints,
there'll be fewer fsyncs if you increase the slru buffer size - as
there'll often be clean buffers due to the checkpoint having written
them out.

Greetings,

Andres Freund