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SubjectRe: 2.6.0 performance problems
On Mon, 29 Dec 2003, Linus Torvalds wrote:

>
>
> On Mon, 29 Dec 2003, Thomas Molina wrote:
> >
> > I just finished a couple of comparisons between 2.4 and 2.6 which seem to
> > confirm my impressions. I understand that the comparison may not be
> > apples to apples and my methods of testing may not be rigorous, but here
> > it is. In contrast to some recent discussions on this list, this test is
> > a "real world" test at which 2.6 comes off much worse than 2.4.
>
> Are you sure you have DMA enabled on your laptop disk? Your 2.6.x system
> times are very high - much bigger than the user times. That sounds like
> PIO to me.

It certainly looks like DMA is enabled. Under 2.4 I get:

[root@lap root]# hdparm /dev/hda

/dev/hda:
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 = 2584/240/63, sectors = 39070080, start = 0


Under 2.6 I get:

[root@lap root]# hdparm /dev/hda

/dev/hda:
multcount = 16 (on)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 38760/16/63, sectors = 39070080, start = 0


Relevant items from my 2.6 configuration file:

CONFIG_GENERIC_ISA_DMA=y
CONFIG_BLK_DEV_IDEDMA_PCI=y
# CONFIG_BLK_DEV_IDEDMA_FORCED is not set
CONFIG_IDEDMA_PCI_AUTO=y
# CONFIG_IDEDMA_ONLYDISK is not set
# CONFIG_IDEDMA_PCI_WIP is not set
CONFIG_BLK_DEV_ADMA=y
CONFIG_BLK_DEV_IDEDMA=y
# CONFIG_IDEDMA_IVB is not set
CONFIG_IDEDMA_AUTO=y
# CONFIG_DMA_NONPCI is not set

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