| From: | Claudio Freire <klaussfreire(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru>, Anastasia Lubennikova <lubennikovaav(at)gmail(dot)com>, PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Vacuum: allow usage of more than 1GB of work mem |
| Date: | 2017-04-11 18:59:56 |
| Message-ID: | CAGTBQpaJY5aY6mF9L7O64dt0CHzzkjnVXtnb6sGDnn3JbaqbYA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Apr 11, 2017 at 3:53 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> 1TB / 8kB per page * 60 tuples/page * 20% * 6 bytes/tuple = 9216MB of
> maintenance_work_mem
>
> So we'll allocate 128MB+256MB+512MB+1GB+2GB+4GB which won't be quite
> enough so we'll allocate another 8GB, for a total of 16256MB, but more
> than three-quarters of that last allocation ends up being wasted.
> I've been told on this list before that doubling is the one true way
> of increasing the size of an allocated chunk of memory, but I'm still
> a bit unconvinced.
There you're wrong. The allocation is capped to 1GB, so wastage has an
upper bound of 1GB.
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