| From: | "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> |
|---|---|
| To: | 'Amit Kapila' <amit(dot)kapila16(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Remove the comment on the countereffectiveness of large shared_buffers on Windows |
| Date: | 2016-11-15 01:44:01 |
| Message-ID: | 0A3221C70F24FB45833433255569204D1F64035F@G01JPEXMBYT05 |
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From: pgsql-hackers-owner(at)postgresql(dot)org
> [mailto:pgsql-hackers-owner(at)postgresql(dot)org] On Behalf Of Amit Kapila
> Okay, not a problem. However, I am not sure the results in this thread
> are sufficient proof as for read-only tests, there is no noticeable win
> by increasing shared buffers and read-write tests seems to be quite short
> (60 seconds) to rely on it.
I think the reason why increasing shared_buffers didn't give better performance for read-only tests than you expect is that the relation files are cached in the filesystem cache. The purpose of this verification is to know that the effective upper limit is not 512MB (which is too small now), and I think the purpose is achieved. There may be another threshold, say 32GB or 128GB, over which the performance degrades due to PostgreSQL implementation, but that's another topic which also applies to other OSes.
How about 3 minutes for read-write tests? How long do you typically run?
Regards
Takayuki Tsunakawa
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