Re: transaction backoff problems (ITS#2741)

[jongchoi@OpenLDAP.org]

> While running test008 with a large number of iterations (-l 2000) I see
the
> operation throughput decrease over time. There are long idle periods when
all
> slapd threads are asleep, and then a short burst of activity accompanied
with
> DEADLOCk messages, and then another long idle period. At least one thread
ought
> to be active at all times, but it appears that all the writers have gone
to
> sleep, for approximately equal amounts of time.
>

Looks it is related to the transaction backoff patch.
In fact, the paramters of the transaction backoff themselves need to
be self adjusted. For example, with a parateter set empirically optimized
for back-bdb does not work well with back-hdb, because they have
different intensity of contention.
Maybe higher randomness or throttling is needed, but I guess that this is
the case
in which the contention is too high, that even backoff doesn't help
(I'm not familiar with -I option, though).
Without backoff, we might see even more contention.

- Jong