Re: 2.6.0 performance problems

[Martin Schlemmer]

On Tue, 2003-12-30 at 00:58, Thomas Molina wrote:
> 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
> 

Increase your readahead:

 # hdparm -a 8192 /dev/hda


BTW:  As we really do get this question a _lot_ of times, why
      don't the ide layer automatically set a higher readahead
      if there is enough cache on the drive or something?


Thanks,

-- 
Martin Schlemmer

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