Paolo Mantegazza wrote:
>
> Hi Kulwinder,
>
> What about disk IO? I suspect that testing while you run something of
> the type: while "true"; do ls -aR /; done, as I often do is going to
> send you jitter up whatever ethercard you are using.
John Storrs actually tried something similar. He did a loop where he
pinged some location over his ethernet card while running the tests.
These results include this heavy ethernet load.
Also, the IDE disk interface is located on the South PCI Bus Bridge.
Therefore, the disk must make its transfers over the PCI bus just like
the ethernet card. The disk then, is treated just like any other PCI
device. In the South Bridge the IDE interface has its own set of
standard PCI configuration registers, as well as IDE specific
registers. Therefore, the access time of the IDE is also limited by its
own PCI Master Latency Timer Register value, and its master/slave bit
setting. Further, an access in progress can be detected in the IDE
specific registers to allow one to find a safe time to change a disk
from being a master to being a slave device.
> I always refered to jitter with the PC being used by combining real time
> and normal use. When we want to avoid jitter we just setup a single user
> mode and kill all the non needed deamons, getting to an operating
> condition close to the old DOS, and the jitter is far lower. But that is
> just for the more demanding conditions.
I think it is important to consider what kind of setup more demanding
applications may need. Because, people interested in fast hard real
time are also usually willing to use dedicated machines that are
optimally configured, maybe even as embedded systems.
- Kal.
-- [rtl] ---
To unsubscribe:
echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR
echo "unsubscribe rtl <Your_email>" | mail [EMAIL PROTECTED]
---
For more information on Real-Time Linux see:
http://www.rtlinux.org/~rtlinux/
