On Tue, Aug 28, 2001 at 12:02:08AM +1000, Andrew Snow wrote:
>
> What I think would be better would be moving postgresql to a system of
> using memory-mapped I/O. instead of the shared buffer cache, files
> would be directly memory-mapped and the OS would do the caching. I
> can't see this happening though because of platform dependancy, but I
> think its worth another look soon because many unix platforms support
> mmap(). I think it would improve the performance of disk-intensive
> tasks noticeably.
Well, this has other problems. Consider tables that are larger than your
system memory. You'd have to continuously map and unmap different sections.
That can have odd side effects (witness mozilla on linux having 15,000
mapped areas or so...)
You would still however get the advantage that you wouldn't have to copy the
data from the disk buffers to user space, you simply get the disk buffer
mapped into your address space.
I think that for commonly used tables that are under 100K in size (most of
the system tables), this is quite a workable idea. If you don't mind keeping
them mapped the whole time.
--
Martijn van Oosterhout <[EMAIL PROTECTED]>
http://svana.org/kleptog/
> It would be nice if someone came up with a certification system that
> actually separated those who can barely regurgitate what they crammed over
> the last few weeks from those who command secret ninja networking powers.
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