> On Wed, Dec 02, 2020 at 01:20:10PM -0600, Justin Pryzby wrote: > On Wed, Dec 02, 2020 at 08:18:08PM +0100, Dmitry Dolgov wrote: > > > On Wed, Dec 02, 2020 at 12:58:51PM -0500, Tom Lane wrote: > > > So ... one of the things that's been worrying me about this patch > > > from day one is whether it would create a noticeable performance > > > penalty for existing use-cases. I did a small amount of experimentation > > > about that with the v35 patchset, and it didn't take long at all to > > > find that this: > > > --- cut --- > > > > > > is about 15% slower with the patch than with HEAD. I'm not sure > > > what an acceptable penalty might be, but 15% is certainly not it. > > > > > > I'm also not quite sure where the cost is going. It looks like > > > 0001+0002 aren't doing much to the executor except introducing > > > one level of subroutine call, which doesn't seem like it'd account > > > for that. > > > > I've tried to reproduce that, but get ~2-4% slowdown (with a pinned > > backend, no turbo etc). Are there any special steps I've probably > > missed? At the same time, I remember had conducted this sort of tests > > before when you and others raised the performance degradation question > > and the main part of the patch was already more or less stable. From > > what I remember the numbers back then were also rather small. > > Are you comparing with casserts (and therefor MEMORY_CONTEXT_CHECKING) > disabled?
Yep, they're disabled.
