Re: max request size 1024KiB by default?

[Jens Axboe]

On Sat, Jul 24 2004, Lee Revell wrote:
> On Sat, 2004-07-24 at 07:27, Rudo Thomas wrote:
> > > HD info:
> > > /dev/hdc:
> > > 
> > >  Model=Maxtor 6Y160P0, FwRev=YAR41BW0, SerialNo=Y44K8TZE
> > >  Config={ Fixed }
> > >  RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=57
> > >  BuffType=DualPortCache, BuffSize=7936kB, MaxMultSect=16, MultSect=16
> > >  CurCHS=4047/16/255, CurSects=16511760, LBA=yes, LBAsects=268435455
> > >  IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
> > >  PIO modes:  pio0 pio1 pio2 pio3 pio4 
> > >  DMA modes:  mdma0 mdma1 mdma2 
> > >  UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6 
> > >  AdvancedPM=yes: disabled (255) WriteCache=enabled
> > >  Drive conforms to: (null): 
> > 
> 
> Your disk controller must not support that.  It looks like the default
> is 1024KiB or whatever the max your controller supports is:
> 
> drivers/ide/ide-disk.c:
> 
>          if (drive->addressing == 1) { 
>                 ide_hwif_t *hwif = HWIF(drive);
>                 int max_s = 2048; 
> 
>                 if (max_s > hwif->rqsize)
>                         max_s = hwif->rqsize;
> 
>                 blk_queue_max_sectors(drive->queue, max_s); 
>         }

It's the drive. lba28 cannot do more than 256 sectors, while lba48 can
do 65536. The controller only has an impact on this if it's buggy.

-- 
Jens Axboe

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