Re: Load Distributed Checkpoints, take 3

Heikki Linnakangas <heikki@enterprisedb.com> writes:
> Tom Lane wrote:
>> I tend to agree with whoever said upthread that the combination of GUC
>> variables proposed here is confusing and ugly.  It'd make more sense to
>> have min and max checkpoint rates in KB/s, with the max checkpoint rate
>> only honored when we are predicting we'll finish before the next
>> checkpoint time.

> Really? I thought everyone is happy with the current combination, and
> that it was just the old trio of parameters controlling the write, nap
> and sync phases that was ugly. One particularly nice thing about
> defining the duration as a fraction of checkpoint interval is that we
> can come up with a reasonable default value that doesn't depend on your
> hardware.

That argument would hold some water if you weren't introducing a
hardware-dependent min rate in the same patch.  Do we need the min rate
at all?  If so, why can't it be in the same units as the max (ie, a
fraction of checkpoint)?

> How would a min and max rate work?

Pretty much the same as the code does now, no?  You either delay, or not.

            regards, tom lane