[17561] in Kerberos_V5_Development
Re: KDC performance test - lookaside cache impact, testing framework
daemon@ATHENA.MIT.EDU (Ken Raeburn)
Fri Apr 6 13:38:35 2012
Mime-Version: 1.0 (Apple Message framework v1257)
From: Ken Raeburn <raeburn@mit.edu>
In-Reply-To: <4F7E1404.7000503@mit.edu>
Date: Fri, 6 Apr 2012 13:36:57 -0400
Message-Id: <6374BD99-171E-49B5-B352-74C08AF6665C@mit.edu>
To: Greg Hudson <ghudson@mit.edu>
Cc: krbdev@mit.edu, Tom Yu <tlyu@mit.edu>
Content-Type: text/plain; charset="windows-1252"
Errors-To: krbdev-bounces@mit.edu
Content-Transfer-Encoding: 8bit
On Apr 5, 2012, at 17:52, Greg Hudson wrote:
> It would be a fairly simple matter to make a hash table for the
> lookaside cache, which should reduce its cost to much less than the cost
> of processing a request, making it potentially worthwhile.
I'd suggest a btree or something else without the (occasional, but potentially significant) resizing costs. A fixed-size hash table can reduce the cost by a constant factor without the resizing cost, but changing the cost to log N is likely a bigger win. And we've got the db2 code sitting around…
Petr's suggestion of reducing STALE_TIME looks like a good one to me, also. Or perhaps use a heuristic like: If a replay isn't seen in X seconds, assume the client probably got the response, and discard the entry; if there is a replay, there may be a network problem that will cause more replays, so "refresh" the timeout and hang onto the entry until Y seconds after the last replay seen, or until the 5-minute window expires. (With X and Y chosen based on observed behavior of various clients, assumptions about likely faulty network behavior -- misconfigured firewalls dropping all responses would be one obvious case, several-second latency along a network path might be another -- and perhaps config information like how many KDC addresses in the current realm, since that factors into the retry interval in the MIT client code, at least.)
Ken
_______________________________________________
krbdev mailing list krbdev@mit.edu
https://mailman.mit.edu/mailman/listinfo/krbdev
