On Fri, 3 Nov 2000, Mike Galbraith wrote:
> On Thu, 2 Nov 2000, Jens Axboe wrote:
>
> > On Thu, Nov 02 2000, Val Henson wrote:
> > > > > 3) combine this with the elevator starvation stuff (ask Jens
> > > > > Axboe for blk-7 to alleviate this issue) and you have a
> > > > > scenario where processes using /proc/<pid>/stat have the
> > > > > possibility to block on multiple processes that are in the
> > > > > process of handling a page fault (but are being starved)
> > > >
> > > > I'm experimenting with blk.[67] in test10 right now. The stalls
> > > > are not helped at all. It doesn't seem to become request bound
> > > > (haven't instrumented that yet to be sure) but the stalls persist.
> > > >
> > > > -Mike
> > >
> > > This is not an elevator starvation problem.
> >
> > True, but the blk-xx patches help work-around (what I believe) is
> > bad flushing behaviour by the vm.
>
> I very much agree. Kflushd is still hungry for free write
> bandwidth here.
In the LKML tradition of code talks and silly opinions walk...
Attached is a diagnostic patch which gets kflushd under control,
and takes make -j30 bzImage build times down from 12 minutes to
9 here. I have no more massive context switching on write, and
copies seem to go a lot quicker to boot. (that may be because
some of my failures were really _really_ horrible)
Comments are very welcome. I haven't had problems with this yet,
but it's early so... This patch isn't supposed to be pretty either
(hw techs don't do pretty;) it's only supposed to say 'Huston...'
so be sure to grab a barfbag before you take a look.
-Mike
P.S. almost forgot. vmstat freezes were shortened too :-)
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