Poor tasking performance

[Adrian Knoth <adi@thur.de>]

Hi,

I wrote a small proof-of-concept-algorithm which should be implemented
in assembler for a DSP-based hardware solution. Actually it uses
blocking file IO to read and write data from/to named pipes.
(read input data, calculate it, write output data. rate is defined
by the external reading process).

More or less fine, 6% CPU consumption. Yesterday I expanded the
program by a commandline frontend to interactively changing
values (coeffs for the calculation). Therefore I defined the
old serial calculation job as a (one) task and the user interface
as another (the program only has two tasks).

While the calculation "always" runs the user interface shows a
prompt and waits for the completion of Get_Line. When the user
terminates his statement by enter his inputline is parsed and
internal variables are changed accordingly.

Nothing spectacular. In general, it's all the same. Result: 18% CPU.

Is that normal? Only by adding one task which hangs in Get_Line
increases the load so much?

Environment is Linux 2.6.7 with Debian gcc-3.3 (unstable).


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