Re: dma hardware underrun
- From: Bob Hauck <postmaster@xxxxxxxxxxxxxxxxxxxxx>
- Date: Sun, 22 Jul 2007 11:46:39 -0400
On Sun, 22 Jul 2007 22:14:24 +0800, treul <lgijnpuhx@xxxxxxxxx> wrote:
I'm currently experiencing a tough DMA underrun problem.
The system is like:
global bus
||
data-compressor ------||------//---- memory
IDE-PCI harddisk -----||
data-decompressor ----||
data-consumer --------||
||
1. harddisk has the compressed data, read to compressed buffer by DMA1;
2. data-decompressor gets data from compressed buffer by DMA2, and puts
decompressed data to decompressed buffers in ISR;
3. data-consumer eats the decompressed data at an uncompromisable speed;
The data-consumer encounters DMA underrun...
Assuming this is an Intel-based system...
Have you tried turning IDE interrupt unmasking on/off with hdparm (the
-u switch)? It could be that the IDE device disables interrupts for too
long, or alternatively that something else is causing excessive latency
(maybe data-decompressor is doing programmed I/O in the ISR?).
That command masks/unmasks other interrupts during the IDE one, which
works on virtually all modern hardware but used to cause problems on
some back in the day.
You don't say what kernel you are using but SATA uses libata whereas IDE
has in the past used a different driver. That might explain why it
works with SATA. Perhaps the libata driver is just more efficient or
has a different pattern of interrupt masking/unmasking.
Also, how is data-decompressor's driver written? Is it copying and/or
decompressing a lot of data in the ISR? How long does that take, and
are other interrupts disabled during that time?
As for the printf's in the interrupt handler, probably you are just
preventing data-consumer from running as often as it normally would. It
is likely hiding the problem rather than fixing it.
--
-| Bob Hauck
-| "Reality has a well-known liberal bias." -- Stephen Colbert
-| http://www.haucks.org/
.
- Prev by Date: Re: How to set timezone
- Next by Date: Retrieving BIOS Tick count equivalent
- Previous by thread: Question on getimeofday
- Next by thread: Retrieving BIOS Tick count equivalent
- Index(es):
Relevant Pages
|
