[9fans] Fossil/venti performance (Was: Sources Gone?)

[lucio@proxima.alt.za]

> i would imagine that cpu has nothing to do with it and encryption
> would add no overhead at all.  i would image that seeks dominate
> your performance numbers.

Well, there are numerous issues.  The machine is a CPU server booting
off another fossil/venti host; it has its own rather pristine, mostly
unused Plan 9 distribution and a few other fossil partitions of which
only one is backed by venti.  I am hesitantly initialising the dump
partition because I'm not convinced I have the efficient direcory
hierarchy I want to live with.

I can't easily check before fossil is active, but venti takes a long
time to start and by the time the machine is "ready", memory is full
and half of swap is in use :-( During "snap -a" load, context
switching and interrupts tend to swing wildly and swap is often being
accessed (it's on IDE and the drive light can only mean swap access, I
do have DMA active :-)

So I would not use this particular configuration to win any
competitions.

In passing, the first time I did this, I powered the machine down a
few times because I was convinced it had stalled.  That might have
been pessimism on my part, because now that I am monitoring it
(stats), it is clear that it occasionally shows no sign of disk
activity (no seek, load in astronomical places) for long periods, only
to proceed again later.

But I do turn all snaptimes to none, which I superstitiously did the
first time and seemed to make a difference (I bet it didn't, but if
anyone suspects that a dump should finish before another starts, I
have the equipment to test the theory.

++L