hi,

(just going through old mail...)

is this stuff still an issue now after softdeps is poolified
and max_softdeps is increased when desiredvnodes is increased?

-Chuck


On Thu, Feb 22, 2001 at 10:28:08PM +0100, Frank van der Linden wrote:
> On Tue, Feb 20, 2001 at 02:27:57PM +0100, Paul Kranenburg wrote:
> > I should amend this. A process pacing itself by sleeping in request_cleanup()
> > is woken up already after softdep_process_worklist() has run (once); fiddling
> > with `tickdelay' probably isn't worth the effort anyway.
> > 
> > One further remark: since softdep worklist processing is handled by the
> > syncer process entirely, there's a severe risk of context switch trashing
> > when the worklist queue is allowed to hover around `max_softdep' threshold,
> > in which case the syncer process will be doing "rush jobs" all the time.
> > 
> > There should probably be some "hysteresis loop" that forces enough
> > worklist processing until the resource allocation is well below
> > the designated maximum.
> 
> The only way to enforce the upper limit would be to check for it
> before each dependency addition, and wait for it to drop if it's
> too high. However, you may be holding some (vnode) locks at that
> point, which the syncer might also want, also the upper loop
> does check for locked vnodes.
> 
> Having softdep_process_worklist() just go on until it's below
> the limit again would mostly work, then again, there's a risk
> that you go through the roof before it gets to run (though
> this might be mostly theoretical)
> 
> A recent change to the FreeBSD code makes dependency cleanups
> also happen from other processes, with some additional hacks
> to see if no deadlocks occur.
> 
> All methods seem a bit messy. I keep thinking "there must be
> a better way to do all this", but that's easy to say, since
> I haven't actually found a better method :-)
> 
> - Frank
> 
> -- 
> Frank van der Linden                           fvdl@wasabisystems.com
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