On Fri, Sep 11, 2020 at 9:34 AM Michael Paquier <mich...@paquier.xyz> wrote: > > On Thu, Sep 10, 2020 at 08:06:10PM +0200, Julien Rouhaud wrote: > > The TPS is obviously overall extremely bad, but I can see that the submitted > > version added an overhead of ~3.9% (average of 5 runs), while the version > > without the optimisation added an overhead of ~6.57%. > > Okay, so that stands as a difference. I am planning to run some > benchmarks on my end as well, and see if I can see a clear > difference.
Thanks! > > This is supposed to be a relatively fair benchmark as all the data are > > cached > > on the OS side, so IO done while holding the bufmapping lock aren't too > > long, > > but we can see that we already get a non negligible benefit from this > > optimisation. Should I do additional benchmarking, like dropping the OS > > cache > > and/or adding some write activity? This would probably only make the > > unoptimized version perform even worse. > > It would be also interesting to see the case where the pages are not > in the OS cache and see how bad it can get. For the read-write case, > I am not sure as we may have some different overhead that hide the > noise. Also, did you run your tests with the functions scanning at > full speed, with (ChecksumCostDelay < 0) so as there is no throttling? I used all default settings, but by default checksum_cost_delay is 0 so there shouldn't be any throttling.
