Re: 2.6.0 performance problems

[Thomas Molina <tmolina@cablespeed.com>]

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