|Subject||RE: [firebird-support] Classic vs Superserver|
> > > (3) Do these motivations make sense?At the moment, SuperServer uses pseudo-threading, not true threading.
> > Yes and no. ;-]
> > Classic does not provide the fastest performance, but it does provide
> > the most consistent multi-connection performance. It is currently (v3
> > will be changing this) the only engine which truly scales across CPUs.
> This is something I don't understand. Superserver uses a thread per
> connection, no? So what is there to stop each thread running on its own CPU
> (until we run out of CPUs), thus scaling across CPUs in the expected fashion?
> - I couldn't find a clear answer to that in the documentation.
> (We're unlikely to have many more active connections than CPUs.)
> > Garbage Collection is performed actively, but if you have goodThis sounds like you are running into the automation database sweep, what is the sweep interval for the database?
> > transaction management, the real overhead is not that bad. The biggest
> > cost of Garbage Collection is that it generates disk writes, which
> > will need to go to disk, which is a slow process. A good disk
> > controller cache with protected write-back cache will eliminate that cost.
> Sorry, but I don't understand "if you have good transaction management the
> real overhead is not that bad".
> I need to do some more work, but what we think is going on at the moment
> (1) there are lots of tiny transactions which update individual records in a
> table, and this goes on all the time
> (2) occasionally something happens which does a scan of that table (or
> otherwise looks at lots of records in a single transaction)
> (3) the first time this "occasional" thing happens it takes an appallingly long
> time and the stats show lots of page writes
> (4) if we immediately re-run this "occasional" thing it behaves more as we
> would expect.
> We think that the writes in (3) are a clue that there's garbage collection going
> on? Why else would a SELECT query cause lots of writes?
It should be disabled and replaced with schedule task/cron job, which performs a sweep during off-peak hours.