On Tue, Oct 01 2002, Con Kolivas wrote:
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> On Tuesday 01 Oct 2002 8:20 pm, Andrew Morton wrote:
> > Jens Axboe wrote:
> > > On Mon, Sep 30 2002, Andrew Morton wrote:
> > > > > io_load:
> > > > > Kernel Time CPU Ratio
> > > > > 2.4.19 216.05 33% 3.19
> > > > > 2.5.38 887.76 8% 13.11
> > > > > 2.5.38-mm3 105.17 70% 1.55
> > > > > 2.5.39 229.4 34% 3.4
> > > > > 2.5.39-mm1 239.5 33% 3.4
> > > >
> > > > I think I'll set fifo_batch to 16 again...
> > >
> > > As not to compare oranges and apples, I'd very much like to see a
> > > 2.5.39-mm1 vs 2.5.39-mm1 with fifo_batch=16. Con, would you do that?
> > > Thanks!
> >
> > The presence of /proc/sys/vm/fifo_batch should make that pretty easy.
>
> Thanks. That made it a lot easier and faster, and made me curious enough to
> create a family or very interesting results. All these are with 2.5.39-mm1
> with fifo_batch set to 1->16, average of three runs. The first result is the
> unmodified 2.5.39-mm1 (fifo_batch=32).
Ah excellent, thanks a lot!
> io_load:
> Kernel Time CPU% Ratio
> 2.5.39-mm1 239.5 32 3.54
> 2539mm1fb16 131.2 57 1.94
> 2539mm1fb8 109.1 68 1.61
> 2539mm1fb4 146.4 51 2.16
> 2539mm1fb2 112.7 65 1.67
> 2539mm1fb1 125.4 60 1.85
>
> What's most interesting is the variation was small until the number was <8;
> then the variation between runs increased. Dare I say it there appears to be
> a sweet spot in the results.
Yes it's an interesting curve. What makes it interesting is that 8 is
better than 16. Both allow one seek to be dispatched, they only differ
in the streamed amount of data we allow to dispatch. 8 will give you
either 1 seek, or 8*256 == 2048 sectors == 1MiB. 16 will give you 1 seek
or 2MiB of streamed I/O.
Tests with other io benchmarks need to be considered as well. And I need
a bit of time to digest this :-). The 8 vs 16 numbers are not what I
expected.
But the deadline io scheduler looks damn good in this test, if I have to
say so myself.
-- Jens Axboe- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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