https://qa.mandrakesoft.com/show_bug.cgi?id=611
Product: kernel
Component: kernel
Summary: UDMA not working properly since kernel 2.4.20.0.5mdk
with i845 chipset
Version: 2.4.20-1mdk
Platform: PC
OS/Version: All
Status: UNCONFIRMED
Severity: major
Priority: P2
AssignedTo: [EMAIL PROTECTED]
ReportedBy: [EMAIL PROTECTED]
Since kernel 2.4.19, UDMA could been enabled successfully on i845 chipset-based
motherboards.
Up to 2.4.20.0.3mdk kernel, hard drive were performing correctly UDMA transfers.
However, since kernel 2.4.20.0.5mdk (note: 2.4.20.0.4mdk was not tested) and
2.4.20.1mdk kernels, UDMA can still be enabled on i845 motherboards, but hard
drive performance is irregular.
It seems that using buffer cache of the disk before a read/write transfer
decrease the transfer performance to non-UDMA levels.
Examples :
IDE hard drive
Model=HITACHI_DK23DA-20, FwRev=00J2A0A1, SerialNo=11L0V8
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4
BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=39070080
IORDY=yes, tPIO={min:240,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=yes: mode=0x80 (128) WriteCache=enabled
Drive conforms to: ATA/ATAPI-5 T13 1321D revision 3: 2 3 4 5
multcount = 16 (on)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 8 (on)
geometry = 2432/255/63, sectors = 39070080, start = 0
1) with kernel 2.4.20.0.3mdk
hdparm -Tt /dev/hda
/dev/hda:
Timing buffer-cache reads: 128 MB in 0.37 seconds =345.95 MB/sec
Timing buffered disk reads: 64 MB in 2.78 seconds = 23.02 MB/sec
This result was consistent with the 2.4.20.0.3mdk kernel.
2) But with kernel 2.4.20.1mdk
hdparm -t /dev/hda
Timing buffered disk reads: 64 MB in 4.61 seconds = 13.88 MB/sec
but it gives irregular results comprised between 10 to 20
and
hdparm -Tt /dev/hda
/dev/hda:
Timing buffer-cache reads: 128 MB in 0.37 seconds =345.95 MB/sec
Timing buffered disk reads: 64 MB in 6.55 seconds = 9.77 MB/sec
Giving consistently about 9MB/sec, the same result as if UDMA was not enabled.
This result is always obtained if a buffer-cache read is performed before the
disk read.
This could be verified with hdparm tests, but on a normal use basis, this
globally cripples hard drive performance on that hardware.
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