Andres Freund <> writes:
> On 2014-09-29 16:16:38 -0400, Tom Lane wrote:
>> I wonder why it's a fixed constant at all, and not something like
>> "wal_buffers / 8".

> Because that'd be horrible performancewise on a system with many
> wal_buffers. There's several operations where all locks are checked in
> sequence (to see whether there's any stragglers that need to finish
> inserting) and even some where they're acquired concurrently (e.g. for
> xlog switch, checkpoint and such).

Hm.  Well, if there are countervailing considerations as to how large is a
good value, that makes it even less likely that it's sensible to expose
it as a user tunable.  A relevant analogy is that we don't expose a way
to adjust the number of lock table partitions at runtime.

                        regards, tom lane

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