Wiki editor request

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От yigong hu
Тема Wiki editor request
Дата
Msg-id CAOxFffdaBFkCryxhutHAtq9WTxiuxjpVW8Utuq0=4rCPhuzpig@mail.gmail.com
обсуждение исходный текст
Ответы Re: Wiki editor request  (Christophe Pettus <xof@thebuild.com>)
Список pgsql-www
Hi,
   Would it be possible to get editor permission on the Postgres wiki? My community account name is yigonghu.
Here is a minor change I’ve wanted to make as I browse the wiki:

  The PostgreSQL manual contains the following paragraph https://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server about the log_statement configuration:

>       "Using all in production leads to severe performance penalties."

 The description mentions that "all" log_statement would cause performance penalties in production mode but in the testing, I found that setting log_statement to all will not cause performance loss under write-intensive workload unless the synchronous_commit is off. Also, it seems that setting log_statement to another value wouldn' cause performance regression but in my testing, I found that the "mod" log_statement would cause a performance loss if the synchronous_commit is off. Thus, I would suggest to elaborate on this description further as:

> "Using all or mod in production would lead to severe performance penalties under some workload. Turning the synchronous_commit to off would cause a more severe performance regression"

Rationale:
    I test the log_statement on PostgreSQL 11.0. The PostgreSQL is running on hardware: 40 vCPU, 64 GB ram, 10GB network, and 1TB HDD. The OS is ubuntu 16.04.
    I first run a read-intensive workload with different log_statment setting. The result shows that for all log_statment, the average latency per query is 7.18ms. For the "mod" statement, the average latency per query is 2.9ms. For the "none" log_statement, the average latency per query is 2.95ms. The result is consistent with the description that  "all" log statement would cause performance penalties. However, when I test on a write-intensive workload, the result shows that for the "all" log_statment, the average latency per query is 8.51ms. For the "mod" statement, the average latency per query is 8.53ms. For the "none" log_statement, the average latency per query is 8.68ms. It seems that there are no performance penalties for the write workload if you are using "all" log statement.
   Also, if I set the synchronous_commit to off and rerun the write-intensive workload, For the "all" log_statment, the average latency per query is 0.71ms. For the "mod" statement, the average latency per query is 0.71ms. For the "none" log_statement, the average latency per query is 0.19ms. This seems to suggest that if closing the synchronous_commit would introduce performance penalties to all and mod log statements.

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