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SubjectRe: 2.4.14-pre6
On Sat, 3 Nov 2001, Linus Torvalds wrote:

> On Sat, 3 Nov 2001, Mike Galbraith wrote:
> >
> > > Otherwise -pre5aa1 still seems to be the fastest kernel *in this test*.
> >
> > My box agrees. Notice pre5aa1/ac IO numbers below. I'm getting
> > ~good %user/wallclock with pre6/pre7 despite (thrash?) IO numbers.
>
> Well, pre7 gets the second-best numbers, and the reason I really don't
> like pre5aa1 is that since pre4, the virgin kernels have had all mapped
> pages in the LRU queue, and can use that knowledge to decide when to
> start swapping.
>
> So in those kernels, the balance between scanning the VM tables and
> scanning the regular unmapped caches is something that is strictly
> deterministic, which is something I _really_ want to have.
>
> We've had too much trouble with the "let's hope this works" approach.
> Which is why I want the anonymous pages to clearly show up in the
> scanning, and not have them be these virtual ghosts that only show up when
> you start swapping stuff out.
>
> Your array cut down to just the ones that made the benchmark in under 8
> minutes makes it easier to read, and clearly pre6+ seems to be a bit _too_
> swap-happy. I'm trying the "dynamic max_mapped" approach now.

Swap-happy doesn't bother this load too much. What it's really sensitive
to is pagein. Turning the cache knobs (vigorously:) in aa-latest...

2.4.14-pre6aa1
real 8m29.484s
user 6m38.650s
sys 0m27.940s

user : 0:06:45.45 70.6% page in : 641298
nice : 0:00:00.00 0.0% page out: 634494
system: 0:00:41.73 7.3% swap in : 118869
idle : 0:02:06.90 22.1% swap out: 154141

echo 2 > /proc/sys/vm/vm_mapped_ratio
echo 128 > /proc/sys/vm/vm_balance_ratio

real 7m25.069s
user 6m37.390s
sys 0m27.540s

user : 0:06:43.60 78.7% page in : 588488
nice : 0:00:00.00 0.0% page out: 514865
system: 0:00:40.47 7.9% swap in : 118738
idle : 0:01:08.92 13.4% swap out: 122340

..lowers the sleep time noticibly despite swapin remaining constant.

-Mike

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