On Sun, Jan 21, 2001 at 10:51:12AM +0000, Alan Chandler wrote:
> On Sat, 20 Jan 2001 20:18:34 -0500 (EST), you wrote:
>
>
> >that's not the topic: Andre's talking about pci-clock-based timing
> >constants the the driver programs into the ide controller - a matter
> >of an extra few/more nanoseconds.
>
> I know, but when looking hard for a problem in one place and not
> finding it, it is sometimes helpful to consider other options.
>
> I am getting errors under 2.4.0 which didn't appear in 2.2.17 - and as
> far as I could see from hdparm - both were at UDMA mode 2 (I assume
> thats what the * means - the man page wasn't very clear). My drives
> only handle up to this mode, and I was wondering if the new driver was
> trying to run them at a mode higher than they were supposed to go.
>
> This massive difference in timing seemed significant.
No, but to me it seems that even though UDMA2 mode is selected in the
drive in 2.2.17 (that's what the * means), the kernel doesn't use DMA,
and thus everything works in PIO4. This would well explain the speed
difference.
> >quite slow in either case, at least for modern hardware (which is
> >all in the 20-40 MB/s range). this looks like a PIO vs DMA difference
> >to me, not even UDMA. of course, hdparm can tell you what mode you're in.
>
> I did discover a difference - 2.2.17 set the drives with multisector
> off, 2.4.0 was setting multisector on.
Multisector is valid only in PIO modes. If both were doing some kind of
DMA, it wouldn't change anything.
> However, I have redone the
> timing with multisector turned on in the 2.2.17 case and the
> difference is still there.
>
> Under 2.2.17 with multisector turned on
>
>
> /dev/hda:
>
> Model=IBM-DHEA-38451, FwRev=HP8OA20C, SerialNo=SH0SH0X1795
> Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
> RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=28
> BuffType=3(DualPortCache), BuffSize=472kB, MaxMultSect=16,
> MultSect=16
> DblWordIO=no, OldPIO=2, DMA=yes, OldDMA=2
> CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=16514064
> tDMA={min:120,rec:120}, DMA modes: sword0 sword1 sword2 mword0 mword1
> mword2
> IORDY=on/off, tPIO={min:240,w/IORDY:120}, PIO modes: mode3 mode4
> UDMA modes: mode0 mode1 *mode2
>
> ------------------
>
> /dev/hda:
> Timing buffered disk reads: 64 MB in 19.88 seconds = 3.22 MB/sec
>
>
> Under 2.4.0
>
>
> /dev/hda:
>
> Model=IBM-DHEA-38451, FwRev=HP8OA20C, SerialNo=SH0SH0X1795
> Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
> RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=28
> BuffType=3(DualPortCache), BuffSize=472kB, MaxMultSect=16,
> MultSect=16
> DblWordIO=no, OldPIO=2, DMA=yes, OldDMA=2
> CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=16514064
> tDMA={min:120,rec:120}, DMA modes: sword0 sword1 sword2 mword0 mword1
> mword2
> IORDY=on/off, tPIO={min:240,w/IORDY:120}, PIO modes: mode3 mode4
> UDMA modes: mode0 mode1 *mode2
>
> ------------------
>
> /dev/hda:
> Timing buffered disk reads: 64 MB in 6.58 seconds = 9.73 MB/sec
>
>
>
> I don't suppose the fact that my hdparm is oldish (3.6 I think) have
> any bearing on this?
No, 3.6 is OK I think.
--
Vojtech Pavlik
SuSE Labs
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