Re: [HACKERS] Re: [QUESTIONS] How to use memory instead of hd?

>
> Bruce Momjian wrote:
> >
> > >
> > > Hi All
> > >
> > > I just upgraded to 128MB RAM, and really don't need ALL of it MOST of the
> > > time, and the main reason for it was to help with database speed.
> > >
> > > But then I got to thinking, is there a way to just semi-permently put a
> > > database into RAM? so that when a query is done it goes only to the image
> > > of the database in RAM, never even touching the hard drive.  This would be
> > > enormasly faster on 50 ~ 100 (or what ever) MB databases, especially on
> > > those new boxes with that 6? or 10? nano second RAM.  Especially if one
> > > could pick and chose which table(s) to put in RAM
> >
> > You can tune your OS to use most of that as buffer cache.  However,
> > writes will be flushed to disk by postgresql fync, or the OS syncing
> > every so often, but not too bad.  You can also up your postgres shared
> > memory buffers, though some OS's have a limit on that.
>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>                                    ^^^^^^^^^^^^^^^^^^^^
> Could we use mmap (instead of shmem) with MAP_ANON flag to get more memory
> for shared buffer pool ?
> I'm using FreeBSD, man mmap says:
>
>      MAP_ANON    Map anonymous memory not associated with any specific file.
>                  The file descriptor used for creating MAP_ANON regions is
>                  used only for naming, and may be specified as -1 if no name
>                  is associated with the region.
>
> Vadim

Yes, we could.  I don't think we do because we an anon-mapped region is
the same as shmem, but if the limit is higher for anon mmap, we could
used it.


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