Re: Redesigning checkpoint_segments

On 06/07/2013 01:00 AM, Josh Berkus wrote:
> Daniel,
>
> So your suggestion is that if archiving is falling behind, we should
> introduce delays on COMMIT in order to slow down the rate of WAL writing?
Delaying commit wouldn't be enough; consider a huge COPY, which can
produce a lot of WAL at a high rate without a convenient point to delay at.

I expect a delay after writing an xlog record would make a more suitable
write-rate throttle, though I'd want to be sure the extra branch didn't
hurt performance significantly. Branch prediction hints would help;
since we don't *care* if the delay branch is slow and causes pipeline
stalls, tagging the no-delay branch as likely would probably deal with
that concern for supported compilers/platforms.

-- Craig Ringer                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services