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SubjectRe: Disk Performance
On Fri, Nov 09, 2001 at 04:20:28PM -0700, Erik Andersen wrote:
> On Fri Nov 09, 2001 at 08:57:07PM -0200, Rik van Riel wrote:
> > >
> > > But wouldn't it make more sense to enable DMA by default, except
> > > for a set of blacklisted chipsets, rather then disabling it for
> > > everybody just because some older chipsets are crap?
> >
> > The kernel does this, but only if CONFIG_IDEDMA_AUTO
> > is enabled ...
>
> That seems to be the theory. In practice every system in my house has
> that option enabled and yet only some controllers boot up with DMA enabled...
>
> For example lets look at the following case. This system has
> an intel chipset builtin and a Promise PCI card.
>
> Uniform Multi-Platform E-IDE driver Revision: 6.31
> ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
> PIIX4: IDE controller on PCI bus 00 dev 39
> PIIX4: chipset revision 1
> PIIX4: not 100% native mode: will probe irqs later
> ide0: BM-DMA at 0xf000-0xf007, BIOS settings: hda:DMA, hdb:DMA
> ide1: BM-DMA at 0xf008-0xf00f, BIOS settings: hdc:DMA, hdd:DMA
> PDC20267: IDE controller on PCI bus 00 dev 68
> PCI: Found IRQ 5 for device 00:0d.0
> PDC20267: chipset revision 2
> PDC20267: not 100% native mode: will probe irqs later
> ide2: BM-DMA at 0xbc00-0xbc07, BIOS settings: hde:DMA, hdf:DMA
> ide3: BM-DMA at 0xbc08-0xbc0f, BIOS settings: hdg:pio, hdh:DMA
> hda: IBM-DPTA-373420, ATA DISK drive
> hdd: PCRW804, ATAPI CD/DVD-ROM drive
> hde: IBM-DTLA-307045, ATA DISK drive
> hdg: IBM-DTLA-307045, ATA DISK drive
> ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
> ide1 at 0x170-0x177,0x376 on irq 15
> ide2 at 0xac00-0xac07,0xb002 on irq 5
> ide3 at 0xb400-0xb407,0xb802 on irq 5
> hda: 66055248 sectors (33820 MB) w/1961KiB Cache, CHS=4111/255/63, UDMA(33)
> hde: 90069840 sectors (46116 MB) w/1916KiB Cache, CHS=89355/16/63
> hdg: 90069840 sectors (46116 MB) w/1916KiB Cache, CHS=89355/16/63
> Partition check:
> hda: hda1 hda2
> hde: hde1
> hdg: hdg1
>
> So the Intel one came up with DMA enabled, No problem there.
>
> The Promise controller has two identical 46.1GB IBM-DTLA-307045 7200
> rpm hard drives on it. The controller is capable of ATA100. The hard
> drives are capable of ATA100. And yet even with CONFIG_IDEDMA_AUTO
> set, these drives both come up running 3.39 MB/s.

Here all drives "default" to UDMA:
(Kernel is 2.4.9 vanilla)
Second Controller is an Promise Ultra 100 TX2

ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
ServerWorks OSB4: IDE controller on PCI bus 00 dev 79
ServerWorks OSB4: chipset revision 0
ServerWorks OSB4: not 100%% native mode: will probe irqs later
ide0: BM-DMA at 0xffa0-0xffa7, BIOS settings: hda:DMA, hdb:pio
ide1: BM-DMA at 0xffa8-0xffaf, BIOS settings: hdc:pio, hdd:pio
PDC20268: IDE controller on PCI bus 02 dev 08
PDC20268: chipset revision 1
PDC20268: not 100%% native mode: will probe irqs later
PDC20268: ROM enabled at 0xfebf8000
PDC20268: (U)DMA Burst Bit ENABLED Primary PCI Mode Secondary MASTER Mode.
ide2: BM-DMA at 0xef90-0xef97, BIOS settings: hde:pio, hdf:pio
ide3: BM-DMA at 0xef98-0xef9f, BIOS settings: hdg:pio, hdh:pio
hda: IBM-DTTA-351010, ATA DISK drive
hde: IBM-DTLA-307045, ATA DISK drive
hdf: IBM-DTLA-307045, ATA DISK drive
hdg: WDC WD1000BB-32CCB0, ATA DISK drive
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
ide2 at 0xefe0-0xefe7,0xefae on irq 24
ide3 at 0xefa0-0xefa7,0xefaa on irq 24
hda: 19807200 sectors (10141 MB) w/466KiB Cache, CHS=1232/255/63, UDMA(33)
hde: 90069840 sectors (46116 MB) w/1916KiB Cache, CHS=89355/16/63, UDMA(100)
hdf: 90069840 sectors (46116 MB) w/1916KiB Cache, CHS=89355/16/63, UDMA(100)
hdg: 195371568 sectors (100030 MB) w/2048KiB Cache, CHS=193821/16/63, UDMA(100)








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