Re: suboverflowed subtransactions concurrency performance optimize

On Tue, 30 Nov 2021 at 12:19, Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> wrote:
>
> On Mon, 30 Aug 2021 at 11:25, Andrey Borodin <x4mmm(at)yandex-team(dot)ru> wrote:
> >
> > Hi Pengcheng!
> >
> > You are solving important problem, thank you!
> >
> > > 30 авг. 2021 г., в 13:43, Pengchengliu <pengchengliu(at)tju(dot)edu(dot)cn> написал(а):
> > >
> > > To resolve this performance problem, we think about a solution which cache
> > > SubtransSLRU to local cache.
> > > First we can query parent transaction id from SubtransSLRU, and copy the
> > > SLRU page to local cache page.
> > > After that if we need query parent transaction id again, we can query it
> > > from local cache directly.
> >
> > A copy of SLRU in each backend's cache can consume a lot of memory.
>
> Yes, copying the whole SLRU into local cache seems overkill.
>
> > Why create a copy if we can optimise shared representation of SLRU?
>
> transam.c uses a single item cache to prevent thrashing from repeated
> lookups, which reduces problems with shared access to SLRUs.
> multitrans.c also has similar.
>
> I notice that subtrans. doesn't have this, but could easily do so.
> Patch attached, which seems separate to other attempts at tuning.

Re-attached, so that the CFapp isn't confused between the multiple
patches on this thread.

--
Simon Riggs http://www.EnterpriseDB.com/