Re: AW: [HACKERS] mmap and MAP_ANON

Andreas Zeugswetter wrote:
>
> >> - Could we use mmap:ing of files at a higher level then
> >> src/backend/strorage/ipc/ipc.c to get even better performance
> >> and cleaness?
> >
> >Yes, we could use mmap() to map the actual files. I will post time
> >timings on this soon.
>
> I do not think this will be a practicable solution, since it would mean the whole db
> has to mmap'ed. This means there has to be enough virtual memory to hold
> the complete database, or at least one table at a time. Or do I understand this wrong ??

Why would we map the whole database or even a whole table?
You can map the section of a file you are interested in.

# man mmap

Besides a sensible memory manager does not actually map the pages
until they are access, unfort. not all OSes are sensible.

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Göran Thyni, sysadm, JMS Bildbasen, Kiruna