Re: CLOG contention

On Sat, Dec 24, 2011 at 9:25 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Thu, Dec 22, 2011 at 4:20 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

>> Also, if it is that, what do we do about it?  I don't think any of the
>> ideas proposed so far are going to help much.
>
> If you don't like guessing, don't guess, don't think. Just measure.
>
> Does increasing the number of buffers solve the problems you see? That
> must be the first port of call - is that enough, or not? If not, we
> can discuss the various ideas, write patches and measure them.

Just in case you want a theoretical prediction to test:

increasing NUM_CLOG_BUFFERS should reduce the frequency of the spikes
you measured earlier. That should happen proportionally, so as that is
increased they will become even less frequent. But the size of the
buffer will not decrease the impact of each event when it happens.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
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