Re: [PATCH 6/9] clockpro-clockpro.patch

Peter Zijlstra
2006-02-06T10:07:27Z

> > > Environment: Dell 1850 4GB EM64T CPUx2 HT disabled, x86_64 kernel
> > > Kernel 1: linux-2.6.15-rc5
> > > Kernel 2: linux-2.6.15-rc5 + clockpro patch posted in 2005/12/31
> > > Kernel 3: linux-2.6.15-rc5 + clockpro patch posted in 2005/12/31 +
> > > modification to disable page cache usage from ZONE_DMA
> > > (to rule out possible zone balancing related problem)

> > > n Kernel 1 Kernel 2 Kernel 3
> > > ======================================
> > > 100 373600 298720 395818
> > > 200 385639 272749 272166
> > > 300 371047 243734 262370
> > > 400 367691 213974 169714
> > > 500 147130 126284 103038

> I've built kernels with CONFIG_MM_POLICY_CLOCKPRO enabled and disabled
> and ran the same tests.
>
> n disabled enabled
> ========================
> 100 366962 392283
> 200 342172 393087
> 300 339325 309595
> 400 230029 283340
> 500 121352 132298
>
> The non-clockpro version (left) has got slower in n >= 400, and the
> clockpro version has got faster in n <= 400. The clockpro version is
> still slower than the "kernel 1" for n=300,400. There seem to be a
> few percents of measurement variances, so I shouldn't judge something
> from small differences in values.

Hmm, better but still some ways to go. Thanks for the results.

> > esp. the last patch in the series:
> > http://programming.kicks-ass.net/kernel-patches/page-replace/2.6.16-rc1-3/kswapd-writeout-wait.patch
>
> This change doesn't seem to be related to clockpro. I wonder if (and
> why) it is significant.

Ah, no patch description there yet. What happens is that most of the new
policies (can) require quite a lot of scanning and are hitting:

blk_congestion_wait(WRITE, HZ/10);

way too often without actually having submitted IO.

> I haven't tried but it should be possible to create similar workloads
> by scaling down the arguments to 2read.c.
>
> BTW, I made some detailed measurments with older kernels. I'll mail
> the results later.

Yes, I did that, however your results show a greater decrease in
throughput than I was able to get. Will investigate my setup.

Kind regards,

Peter