Strange IDE performance change in 2.6.1-rc1 (again)

[Paolo Ornati <ornati@lycos.it>]

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As I have already said I have noticed a strange IDE performance change 
upgrading from 2.6.0 to 2.6.1-rc1.

Now I have more data (and a graph) to show: the test is done using
"hdparm -t dev/hda" at various readahead (form 0 to 512).

o SCRIPT

#!/bin/bash

MIN=0
MAX=512

ra=$MIN
while test $ra -le $MAX; do
    hdparm -a $ra /dev/hda > /dev/null;
    echo -n $ra$'\t';
    s1=`hdparm -t /dev/hda | grep 'Timing' | cut -d'=' -f2| cut -d' ' -f2`;
    s2=`hdparm -t /dev/hda | grep 'Timing' | cut -d'=' -f2| cut -d' ' -f2`;
    s=`echo "scale=2; ($s1+$s2)/2" | bc`;
    echo $s;
    ra=$(($ra+16));
done


o RESULTS for 2.6.0  (readahead / speed)

0	13.30
16	13.52
32	13.76
48	31.81
64	31.83
80	31.90
96	31.86
112	31.82
128	31.89
144	31.93
160	31.89
176	31.86
192	31.93
208	31.91
224	31.87
240	31.18
256	26.41
272	27.52
288	31.74
304	27.29
320	27.23
336	25.44
352	27.59
368	27.32
384	31.84
400	28.03
416	28.07
432	20.46
448	28.59
464	28.63
480	23.95
496	27.21
512	22.38


o RESULTS for 2.6.1-rc1  (readahead / speed)

0	13.34
16	25.86
32	26.27
48	24.81
64	26.26
80	24.88
96	27.09
112	24.88
128	26.31
144	24.79
160	26.31
176	24.51
192	25.86
208	24.35
224	26.48
240	24.82
256	26.38
272	24.60
288	31.15
304	24.61
320	26.69
336	24.54
352	26.23
368	24.87
384	25.91
400	25.74
416	26.45
432	23.61
448	26.44
464	24.36
480	26.80
496	24.60
512	26.49


The graph is attached. (x = readahead && y = MB/s)

The kernel config for 2.6.0 is attached (for 2.6.1-rc1 I have just used 
"make oldconfig").

INFO on my HD:

/dev/hda:

 Model=WDC WD200BB-53AUA1, FwRev=18.20D18, SerialNo=WD-WMA6Y1501425
 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
 RawCHS=16383/16/63, TrkSize=57600, SectSize=600, ECCbytes=40
 BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=39102336
 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes:  pio0 pio1 pio2 pio3 pio4
 DMA modes:  mdma0 mdma1 mdma2
 UDMA modes: udma0 udma1 udma2 udma3 *udma4 udma5
 AdvancedPM=no WriteCache=enabled
 Drive conforms to: device does not report version:  1 2 3 4 5

INFO on my IDE controller:

00:04.1 IDE interface: VIA Technologies, Inc. VT82C586/B/686A/B PIPC Bus 
Master IDE (rev 10)


Comments are welcomed.

Bye,

-- 
	Paolo Ornati
	Linux v2.4.23







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