[OpenAFS] cache performance

[Neulinger, Nathan]

> Nathan> What sort of additional logging are you looking for in the
> Nathan> file server?
>=20
> Nathan> Also, how do you plan on handling the "if it's already in the
> Nathan> cache, the file server probably won't see a request" issue?
>=20
> Nathan> Adding more logging is relatively easy to do, just come up
> Nathan> with a list.
>=20
> Well, let me first outline what information we glean from the client
> audits we do today.
>=20
> The goal of our client cache audits is to obtain, for each host, a
> list of the volumes accessed by that client in the last 24 hours, as
> well as the amount of data (not so important, but interesting).  By
> collecting this information for all clients in a given cell, I can
> then determine for each AFS volume in my cell, the list of clients
> that have accessed that volume in the last 24 hours.
>=20
> Today, by auditing the volume headers cell-wide[*], I can=20
> determine the
> lastaccess timestamp, but not the list of clients accessing it.  =20
>=20
> Now, what I would like to get on the fileserver is additional logging
> which allows me to generate this kind of report on a daily basis.
> Additional log entries in the FileLog are probably sufficient, but I
> would be concerned about the volume of information added to the log,
> as well as the logfiles volatility.
>=20
> For example, the default behavior is to save *one* FileLog after a
> restart.  Perform more than one restart in a single day, and you lose
> some logging information.  Actually, the more I think about it, the
> less I like using the FileLog.  We really need a mechanism for
> maintaining these statistics that is more robust.

Have you considered using the -syslog log mechanism, or are you running
on a platform with a syslogd that can't handle heavy loading.=20

> I'm also worried about the volume of information that would be
> generated into the FileLog, which should be the place to look for
> problem diagnostics, which you don't want to hide among a cloud of
> performance/usage statistics.
>=20
> I think a better mechanism would be to have the fileserver maintain
> this information in memory, and to query it (and reset it)
> periodically, via a new RPC.  Then, I can ask for this data as often
> as I want, once a day, or maybe once an hour, if I need to do finer
> grained analysis.

Yeah, that's what Derrick and I were thinking, something similar in
nature to fstrace.

> Phil
>=20
> [*] Bonus question: anyone know where I'm getting these timestamps?
> I'll bet you can't guess...

dayUseDate?

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>=20