On Fri, Jun 03, 2005 at 01:56:11PM -0400, Perry E. Metzger wrote:
> 
> Sean Davis <dive-nb@endersgame.net> writes:
> >> > I don't recall exactly who said what, but I do know that every time I've
> >> > tried NEW_BUFQ_STRATEGY, once I put the system under some heavy load, any
> >> > interactive apps I have running come to a screeching halt (we're talking 30
> >> > second lag between a keystroke and the letter showing up in an xterm here).
> >> >
> >> > Please do not make it the default.
> >> 
> >> Er, that's the behavior I get when I *don't* use NEW_BUFQ_STRATEGY.
> >> Many others have the same complaint. That's why I use it, and that's
> >> why a lot of us would like it as the default.
> >
> > Are you running with softdeps enabled, too?
> 
> Yes.
> 
> > I've had softdeps and new_bufq_strategy bring this system to it's
> > knees when doing a lot of stuff at once - but running without
> > softdeps, without new_bufq_strategy, everything works just fine. (I
> > don't trust softdep in NetBSD; perhaps it's just a -current thing,
> > but it seems that every time I try it, and put the system under
> > serious load, it locks the machine and causes tons of data loss.)

Let me clarify a bit here: I meant "softdeps and/or new_bufq_strategy" -
they both hurt this machine badly. For example, if I have softdeps enabled,
and untar pkgsrc, about 30 seconds later, the machine acts like it's totally
frozen while all the data actually gets written out from RAM.

With NEW_BUFQ_STRATEGY, something similar but not exactly the same
happens... this time, just about any large amount of disk I/O leads to
interactive performance going down the toilet and a "feels hardlocked"
situation as described above. It can be something as simple as copying a few
300 meg files from one disk to another.

> That's really bizarre. First, I've been using softdeps for years now
> without any issues, under a wide variety of kernels. Second, I get
> serious problems with I/O pausing for long periods if I don't turn on
> NEW_BUFQ_STRATEGY....

I agree, it's bizarre. I've talked to tons of people who have no problems
with softdeps at all, and use NEW_BUFQ_STRATEGY without any issues there,
either. I highly doubt it's hardware issue on my side, but who knows... a
storage controller driver not playing well with other code, perhaps? At this
point all I have is guesses, but running !softdep !new_bufq performs quite
well on this machine.

-Sean