[OpenAFS-devel] dealing with rxevent queue stalls

[Mark Vitale]

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On Sep 24, 2013, at 8:02 AM, Derrick Brashear <shadow@gmail.com> wrote:
> I haven't profiled rxevent queue handling in about 5 years. With your =
code does the queue appear "sick" on a normally functioning host if you =
assume that threshold is 0 (if now is later than the top scheduled =
event, assume it should have already fired)?

No, I've currently got a #define for a 5-second "grace" period.  In all =
the cores I've examined, the difference between "now" and the top epoch =
is always about zero for active fileservers, and usually a positive =
number (1-60 secs) for volservers and DB servers.   The only negative =
values I've ever observed were approx -4200 secs (!!!) for the broken =
timer case, and -17 secs for the LWP priority inversion case.  In my =
simulated testing, the 5-second grace period was sufficient to never =
flag a working server as sick, but it correctly flags simulated "sick" =
servers fairly quickly.  So the threshold I've been testing with is =
essentially -5 seconds; but it's implemented in such a way as to provide =
some hysteresis so that the server's not marked "well" until the =
difference is the normal 0 seconds. =20

--
Mark Vitale
mvitale@sinenomine.net


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