Re: IDE DMA slower in 2.3.99pre3 than in 2.2.14 and in 2.0.36

From: Harald Koenig (koenig@tat.physik.uni-tuebingen.de)
Date: Mon Apr 03 2000 - 12:37:16 EST


On Apr 03, Clifford King wrote:

> Alessandro Suardi wrote:
>
> > Alessandro Suardi wrote:
> > >
> > > Seems we're not moving from the 8.6 MB/s marker :(
> > >
> > > 2.3.99pre3 idebus=33 36.99 8.60
> > > multcount=0
> > > 2.3.99pre3 idebus=33 36.89 8.56
> > > multcount=8
> > >
>
> > [section removed]
>
> hdparm no longer gives drive performance numbers that are equivalent
> to 2.2.X kernels on the more recent 2.3.X kernels. hdparm uses disk raw
> I/O calls to measure performance and the 2.3.X kernels have had the disk
> code re-worked to improve overall system response while heavy disk
> I/O is occurring. You need to create your own test say by using the "time"
> command and "dd" to read a file of a known size then, calculte the
> transfer rate from the time report.

at least up to ~16 MB/sec for my UDMA33 system, all tests and kernel versions
(2.2.14 and 2.3.51) with hdparm -Tt report the same transfer rates as dd
and other similar tests, including my own benchmark tool which reads
the whole disk and gives transfer rates for every 10+ MB which gives
very informative (and interesting;) plots. and all those values
match those from a much faster PC with K7 and UDMA66.

trouble for my UDMA33 system starts `only' beyond ~16 MB/sec, and again
I get identical results for all tools, including hdparm with 2.3.51 kernel...

Harald

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