Subject: Re: Interactive responsiveness under heavy I/O load
To: David Brownlee <>
From: Johnny Billquist <>
List: tech-kern
Date: 01/27/2004 21:54:27
On Tue, 27 Jan 2004, David Brownlee wrote:

> On Tue, 27 Jan 2004, Hauke Fath wrote:
> > At 23:43 Uhr +0100 26.1.2004, Johnny Billquist wrote:
> > >>    Softdep is such a huge performance win, especially for tasks like
> > >>    extracting a pkgsrc tree, because lots of metadata writes update
> > >>    the same disk block repetitively (think about adding files one at a
> > >>    time to the same directory). With softdep, each of these updates is
> > >>    done in memory (without the sync disk wait) and the resulting final
> > >>    directory blocks written to disk (again, speaking very broadly).
> > >
> > >softdep:s really sounds nice, but last I tried it (a few months ago) it
> > >still crashed my VAX very predictably, so I'd guess it still isn't good
> > >enough to turn on for people in general.
> >
> > Same here on a SparcStation 10. Both with current and 1.6 kernels, softdep
> > mounts make sure the box locks up during the next /etc/daily run.
> 	I'm running softdeps on a 1.6.1_STABLE, alpha and sparc5 as
> 	reasonably loaded NFS servers, and on 1.6ZI sparc & sparc64 boxes
> 	as NFS clients (twenty or so users).
> 	Also on i386 boxes, but those are less interesting :)
> 	Alpha has been up for 165 days (I forget why it was rebooted),
> 	sparc5 tends to go down every few months. Client boxes running
> 	current are a little harder to benchmark as they keep getting
> 	updated :)
> 	I'm pretty sure there are still softdep problems, or problems
> 	elsewhere exposed by softdeps pushing things harder...

Well, if someone really wanted to take a shot at it, I could provide a
system, and a way of shooting it down by using softdep.

But we're talking slow VAXen here...


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email:           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol