| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
| Subject: | Re: Large writable variables |
| Date: | 2018-10-16 19:13:43 |
| Message-ID: | CA+Tgmobk-6=b2KLRRMUWGNWi9KzKrx=WNszr7DDE+QCuwNyrEQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Oct 15, 2018 at 4:08 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> So we have 500kb of not-initialized memory mapped into every
> process. That's, uh, not nothing.
Thinking about this a bit more, why is this bad? I mean, if the
memory is never touched, the OS does not really need to allocate or
zero any pages, or even make any page table entries. If somebody
actually accesses the data, then we'll take a page fault and have to
really allocate, but otherwise I would think we could have 50MB of
unused bss floating around and it wouldn't really matter, let alone
500kB.
What am I missing?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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