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Re: slowdown when reading from block devices

Wim De Smet said:
> Hi,
> I've noticed in my (woody based) testing/unstable that when I access block
> devices such as (very obvious off course) my hard disk or my cd-rom
> device, my system hangs for short moments. Meaning heavier and longer than
> you would expect it to on an ide system. My kernel version is 2.2.20, I
> have an ata 133 ide interface if that helps any. It's especially annoying
> when ripping a cd and in the mean time trying to play some music (with
> xmms for example). My system is pretty fast in and of its own so the
> hardware shouldn't be an issue.
> Can anybody help me out, maybe something to do with buffers or the likes?

sounds like it could be a DMA issue. What kind of controller? my Promise
ATA/100 controllers have a proc entry in /proc/ide which gives a good
deal of info about the controller, the DMA mode etc..

cat /proc/ide/pdc202xx

                                PDC20267 Chipset.
------------------------------- General Status
Burst Mode                           : enabled
Host Mode                            : Normal
Bus Clocking                         : 66 External
IO pad select                        : 10 mA
Status Polling Period                : 0
Interrupt Check Status Polling Delay : 2
--------------- Primary Channel ---------------- Secondary Channel
                enabled                          enabled
66 Clocking     enabled                          disabled
           Mode PCI                         Mode PCI
                FIFO Empty                       FIFO Empty
--------------- drive0 --------- drive1 -------- drive0 ---------- drive1
DMA enabled:    yes              yes             yes               yes
DMA Mode:       UDMA 4           UDMA 4          NOTSET            NOTSET
PIO Mode:       PIO 4            PIO 4           NOTSET            NOTSET

hdparm can be used to manipulate IDE settings, though honestly I have
never really used it. I turn on DMA in my kernel config(I compile my
own kernels) and never had to use HD parm as far as I can remember.

your controller may have a similar entry in /proc/ide where you can
see the status ..not sure though. I am runing kernel 2.2.19 + ide
patch from www.linux-ide.org.


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