Re: Odd IDE performance drop 2.4 vs 2.6?

From: Ondrej Zary
Date: Fri Jun 17 2005 - 08:46:47 EST

Alan Cox wrote:
On Mer, 2005-06-15 at 20:15, Ondrej Zary wrote:

Now I've tested it with preempt disabled and nothing has changed. When fiddling around with hdparm, I got about 16MB/s max. with 2.6.12-rc5. With 2.4.31, I got about 21MB/s when just the DMA was enabled (read-ahead and multcount set to 0 - changing them does not make almost any difference).

multcount is only used for PIO so that would be expected. Similarly the
block readahead should matter but not anything drive level.

If you compare the hdparm data are both 2.4 and 2.6 selecting the same
IDE modes ?

This is in my init scripts:
/usr/sbin/hdparm -u1c1k1 /dev/hda /dev/hdc /dev/hdd 1> /dev/null
It selects UDMA2 mode in both 2.4 and 2.6.

hdparm -i /dev/hda shows exactly the same output in both 2.4 and 2.6:


Model=WDC WD300BB-00AUA1, FwRev=18.20D18, SerialNo=WD-WMA6W1847372
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=58633344
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
AdvancedPM=no WriteCache=enabled
Drive conforms to: device does not report version:

* signifies the current active mode

Ondrej Zary

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