Re: synchronous commit vs. hint bits

On Mon, Nov 7, 2011 at 6:33 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Mon, Nov 7, 2011 at 5:26 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>
>>> 5. Make the WAL writer more responsive, maybe using latches, so that
>>> it doesn't take as long for the commit record to make it out to disk.
>>
>> I'm working on this already as part of the update for power
>> reduction/group commit/replication performance.
>
> I extracted this from my current patch for you to test.

Thank you!

> Rather useful actually 'cos its allowed me a sensible phasing of the
> development.

+1.

<reads patch>

Hmm, this is different than what I was expecting, although that's not
necessarily bad. What this does is retain wal_writer_delay, but allow
the WAL writer to be woken up more frequently if there's enough WAL to
justify it. What I was expecting you to do is eliminate
wal_writer_delay altogether and drive the wakeups entirely off of the
latch. I think you could get away with that, because SetLatch is
ridiculously cheap if the latch is already set.

Anyway, I'll give this a spin as you have it and see what falls out.

--
Robert Haas
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