Hello Amit.
>> Also, given the heavy UPDATE nature of the pgbench test, a non 100% default
>> fill factor on some tables would make sense.
>
> FWIW, sometime back I have seen that with fill factor 80, at somewhat
> moderate client counts (32) on 192 - Hyper Threaded m/c, the
> performance is 20~30% better, but at higher client counts, it was same
> as 100 fill factor.
The 20-30% figure is consistent with figures I collected 2 years ago about
fill factor on HDD, see the beginning run of:
http://blog.coelho.net/database/2014/08/23/postgresql-fillfactor-and-update.html
Although I found that the advantages is reduced after some time because
once a page has got an update it has some free space which can be taken
advantage of later on, if the space was not reclaimed by vacuum.
I cannot understand why there would be no advantage with more clients,
though...
Alas, performance testing is quite sensitive to many details:-(
--
Fabien.
