Re: [9fans] fidtab revisited

["Ronald G. Minnich" <rminnich@lanl.gov>]

On Mon, 17 Feb 2003, Andrew Simmons wrote:

> Pondering further on fidtab, I was wondering if anyone had any statistics on
> the average and maximum number of fids in the table for any given connection
> to u9fs. Since a hash table was considered appropriate, I would guess that
> quite a few fids were anticipated, but since the current implementation is
> effectively a linked list, I would also guess that there are not that many
> in practice. My interest in this is that I'm tooling around with a knock-off
> of u9fs running as an NT service serving NT files, mainly as an exercise to
> nail down my understanding of how 9p works.


On v9fs on Linux, once the dcache came into the picture, we found fid use
increased to the hundreds, pretty much to the sum of all files opened for
the uptime of the machine, until such time as resources were needed.  We
capped fids at 256 to test our code for handling "out of fids" on the
client (v9fs) side, and there we ran into an interesting problem.  Linux
dcache entry flushing is pretty primitive: you pretty much say 'flush all
them there dcache entries for the superblock' and they all go away
(preferable would be something SunOS did in some areas, which was to say
'try to flush 100 or so of "this thing"' but maybe Linux will improve in
that area).

Since we almost have the 9p2000 client working on linux now, I expect to
get these numbers for u9fs -- I'll let you know.

ron