On Fri, Oct 3, 2014 at 1:40 PM, Bruce Momjian <bruce@momjian.us> wrote:
On Fri, Oct 3, 2014 at 04:11:30PM +0200, Andres Freund wrote: > On 2014-10-03 10:07:39 -0400, Gregory Smith wrote: > > On 10/3/14, 8:26 AM, Andres Freund wrote: > > >#define NUM_XLOGINSERT_LOCKS 1 > > >tps = 52.711939 (including connections establishing) > > >#define NUM_XLOGINSERT_LOCKS 8 > > >tps = 286.496054 (including connections establishing) > > >#define NUM_XLOGINSERT_LOCKS 16 > > >tps = 346.113313 (including connections establishing) > > >#define NUM_XLOGINSERT_LOCKS 24 > > >tps = 363.242111 (including connections establishing) > > > > Just to clarify: that 10% number I threw out was meant as a rough estimate > > for a system with the default configuration, which is all that I tested. It > > seemed like people would likely need to tune all the usual things like > > checkpoint_segments, shared_buffers, etc. as well before seeing much better. > > You did all that, and sure enough the gain went up; thanks for confirming my > > guess. > > > > I still don't think that means this needs a GUC for 9.4. Look at that jump > > from 1 to 8. The low-hanging fruit here hasn't just been knocked off. It's > > been blended into a frozen drink, poured into a glass, and had a little > > paper umbrella put on top. I think that's enough for 9.4. But, yes, let's > > see if we can add delivery to the side of the pool in the next version too. > > So 25% performance on a relatively small machine improvements aren't > worth a GUC? That are likely to be larger on a bigger machine? > > I utterly fail to see why that's a service to our users.
Well, I think the issue is that having a GUC that can't reasonably be tuned by 95% of our users is nearly useless. Few users are going to run benchmarks to see what the optimal value is.
I remember Informix had a setting that had no description except "try different values to see if it helps performance" --- we don't want to do that.
