[openbeos] Re: Threading and File Descriptors
- From: François Revol <revol@xxxxxxx>
- To: openbeos@xxxxxxxxxxxxx
- Date: Sat, 17 Aug 2002 10:30:00 +0200 (MEST)
En réponse à Michael Phipps <mphipps1@xxxxxxxxxxxxxxxx>:
> > [snip]
> Trees and skiplists (both of which I considered) are *way* too big,
> memory and code wise, for kernel work.
> Think about it - skip lists with 2-10 (or more) pointers per node? Where
> a node is a single socket/file handle?
> Trees are possible, but they still have issues (O(log 2 N)) with
> performance, they have to be rebalanced, and they are painful to code.
> Not to mention the 2 pointers per node. I think that the solution for
> these things *has* to be space and code efficient. I am thinking that
> maybe allocating a structure like this:
> struct fewFileHandles{
> fileHandle small[4];
> struct manyFileHandles *more;
> }
>
I see I had similar ideas :)
> Where manyFileHandles is exactly the same, but with, maybe 25
> fileHandles and a pointer to another of the same would be a good
> approach.
> In fact, that sort of thing solves both of these issues. Leaping through
> the list, 25 at a time, is not too bad, for file handles and sockets.
> Maybe 50 pages at a time for VM... Or even:
> struct vmPages {
> page *pages[50];
> a100Pages *somePages;
> a1000Pages *lotsOfPages;
> }
>
> Where one or both of the pointers will be null...
> Hmm - I will have to think about that...
>
IIRC the Ext2 filesystem uses this kind o approach for storing files...
there are direct, indirect and double indirect blocks...
François.
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