[EMAIL PROTECTED] (Hal Murray) writes:
> >I'd like to object: Some long time ago someone (I can't remember) made a test
> >over an extended period of time showing that Linux did not loose a single
> >interrupt. However depending on the drivers and crappy hardware (not to talk
> >about CPU frequency scaling and ACPI's various power saving modes), the
> >system
> >may loose interrupts. For any hardware there is a rate of interrupts that
> >cannot be handled. For my 16MHz 386SX that rate was quite low.
>
> It may depend upon which version/distributino of Linux you are talking
> about.
> I have an old RH 7.2 system. After a reasonably vanilla install,
> it was using PIO for disk accesses. Any big burst of disk activity
> would cause missed interrupts. I have a test hack for measuring
> disk bandwidth. It would totally trash the clock.
> After poking around a bit I found some simple way to activate the
> DMA mechanism. That solved the problem for me.
> I forget the details.
'man hdparm'
Looking at my system, substitute '/dev/hdc' with where your disks are.
# hdparm /dev/hdc
/dev/hdc:
multcount = 16 (on)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on) <******* Shows DMA is on
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 65535/16/63, sectors = 241254720, start = 0
# hdparm -i /dev/hdc % Check where the '*' is in the list of IDE modes.
/dev/hdc:
Model=IC35L120AVVA07-0, FwRev=VA6OA52A, SerialNo=VNC607A6GLWZYJ
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=52
BuffType=DualPortCache, BuffSize=1863kB, MaxMultSect=16, MultSect=16
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=241254720
IORDY=on/off, 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
DMA mode is used
AdvancedPM=yes: disabled (255) WriteCache=enabled
Drive conforms to: ATA/ATAPI-5 T13 1321D revision 1:
* signifies the current active mode
To get DMA working you ofcause need to have support for your IDE
chipset in your kernel.
--
Björn
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