Re: Patch: raise default for max_wal_segments to 1GB - Mailing list pgsql-hackers

From Corey Huinker
Subject Re: Patch: raise default for max_wal_segments to 1GB
Date
Msg-id CADkLM=cAh254172uLf+kh6TBPq9kwPbDF2e+=JgtkQhVOVpdgQ@mail.gmail.com
Whole thread Raw
In response to Re: Patch: raise default for max_wal_segments to 1GB  (Heikki Linnakangas <hlinnaka@iki.fi>)
List pgsql-hackers
Naive question: would it be /possible/ to change configuration to accept percentages, and have a percent mean "of existing RAM at startup time"?

I ask because most of the tuning guidelines I see suggest setting memory parameters as a % of RAM available.

On Tue, Mar 3, 2015 at 1:29 PM, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
On 03/03/2015 08:21 PM, Josh Berkus wrote:
On 03/03/2015 10:15 AM, Josh Berkus wrote:
On 03/02/2015 11:25 PM, Heikki Linnakangas wrote:
I propose that we remove the comment from max_wal_size, and also remove
the "in milliseconds" from wal_receiver_timeout and
autovacuum_vacuum_cost_delay.

+1


Actually, let's be consistent about this.  It makes no sense to remove
unit comments from some settings which accept ms but not others.

Do we want to remove unit comments from all settings which accept
"MB,GB" or "ms,s,min"?  There's more than a few.  I'd be in favor of
this, but seems like (a) it should be universal, and (b) its own patch.

I think it's a good rule that if the commented-out default in the sample file does not contain a unit, then the base unit is in the comment. Otherwise it's not. For example:

#shared_buffers = 32MB                  # min 128kB
                                        # (change requires restart)

The base unit is BLCKSZ, i.e. 8k, but usually people will usually use MB/GB. And that is evident from the default value, 32MB, so there's no need to mention it in the comment.

#tcp_keepalives_idle = 0                # TCP_KEEPIDLE, in seconds;
                                        # 0 selects the system default

Here it's not obvious what the unit should be from the default itself. So the comment says it's "in seconds".

- Heikki



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