From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
Cc: | Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Petr Jelinek <petr(at)2ndquadrant(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
Subject: | Re: reorderbuffer: memory overconsumption with medium-size subxacts |
Date: | 2018-12-16 20:32:25 |
Message-ID: | 20181216203225.rieanqfcf274krno@alap3.anarazel.de |
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Lists: | pgsql-hackers |
Hi,
On 2018-12-16 17:30:30 -0300, Alvaro Herrera wrote:
> On 2018-Dec-16, Andres Freund wrote:
>
> > > I think there's a one-line fix, attached: just add the number of changes
> > > in a subxact to nentries_mem when the transaction is assigned to the
> > > parent.
> >
> > Isn't this going to cause significant breakage, because we rely on
> > nentries_mem to be accurate?
> >
> > /* try to load changes from disk */
> > if (entry->txn->nentries != entry->txn->nentries_mem)
>
> Bahh.
>
> Are you suggesting I should try a more thorough rewrite of
> reorderbuffer.c?
I'm saying you can't just randomly poke at one variable without actually
checking how it's used. I kinda doubt you're going to find something
that's immediately backpatchable here. Perhaps something for master
that's then backpatched after it matured for a while.
Greetings,
Andres Freund
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