Re: overcommit_ratio setting - Mailing list pgsql-performance

From Yi Sun
Subject Re: overcommit_ratio setting
Date
Msg-id CABWY_HDdBH4=BjzVKLRqd1uzOWzyN4sY4c51sfgWJ1km_AgBSg@mail.gmail.com
Whole thread Raw
In response to Re: overcommit_ratio setting  (Laurenz Albe <laurenz.albe@cybertec.at>)
Responses Re: overcommit_ratio setting  (Laurenz Albe <laurenz.albe@cybertec.at>)
List pgsql-performance

On Mon, 2021-06-14 at 18:16 +0800, Yi Sun wrote:
> After checking doc, only mentioned vm.overcommit_memory=2, but didn't mentioned vm.overcommit_ratio recommended value
> https://www.postgresql.org/docs/11/kernel-resources.html#LINUX-MEMORY-OVERCOMMIT
> some articles mentioned that 80 or 90 configuration in their env
> So is it OK just to configure  vm.overcommit_ratio to 90 please?

It depends on the size of RAM and swap space:

overcommit_ratio < (RAM - swap) / RAM * 100

Here, RAM is the RAM available to PostgreSQL.
 
Thank you for your reply

1. Our env RAM are 4GB, 8 GB, 16 GB... as below url suggestion, could we configure swap as below?

RAM                 swap

2GB – 8GB       = RAM
>8GB                8GB

2. If the RAM is 4GB and 8GB, the formula  (RAM - swap) / RAM * 100 result will become to 0, how could we configure overcommit_ratio please?

Thank you

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