Re: [9fans] Different representations of the same file/resource in a synthetic FS

[andrey mirtchovski <mirtchovski@gmail.com>]

> how are the resultant files looked up?  it turns out that generating
> the file hash table was the single most expensive operation for
> upas/fs, given mailboxes with ~10k messages.
> (http://9fans.net/archive/2009/05/106)

still a hash. i'm not doing anything particularly clever for speed,
and it shows in places. listing large directories is the slowest
operation by far, as it would be for most cases where several thousand
"stat" structures would have to be dynamically created for each entry
in a directory. i'm not pre-generating anything however, so in daily
use, where each client knows exactly where to go, i'm not seeing
slowdowns.

not that i'm worried: we recently discovered a few misconfigured
clusters around here (names withheld) that were using ldap and no
local nameservice caching. each stat on those boxes would take 0.05 ms
(instead of 0.005) to complete because it needed to contact a server
for username lookup. the wait became unbearable above a number of
thousands of files in a particular directory, so people finally
started complaining after waiting for minutes for 'ls -l' to finish.
things could be way worse, i guess :)