Re: [9fans] 9P optimization

["Steve Simon" <steve@quintile.net>]

> http://mbgokhale.org/rminnich/job/autocacher/autocache.ps

Interesting idea, I must read up on what else has been published on cacheing
to avoid high latency links.

It would be fun to modify cfs to have a couple of cache coherency algorithms,
the timeout you describe could be one, Boyds ftp cache rule is also interesting -
the timeout value is proportional to how long ago the file was last written, so
old files tend to be stable.

The cache could be dynamic on the device type on which the file lives,
fossil/kfs/kenfs get timeouts, others are assumed to be synthetic files and so
should have their verson numbers checked every time as cfs does now.

We could even implement a /dev/fossilchg file which contains the dirstat(2) info
of all modified files as they change. This would allow persistant (or at least
long lived) connections to attempt to keep a near consistant view of the file.
That is any file which has had an update since the local cfs has been started
would have a known state (be it consistant or inconsisitant); similarly any file
who had to have its version checked would have a known state also.

This is of course a seperate issue to the coelessing of multiple p9 operations
in a single packet as, though as previous posters pointed out it would help cfs too.

my 2¢

-Steve