Why does the prior level change in this case.

I need to undertand why the following works the way it does.

When I do something like

Quote:

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cat < /dev/zero | grep "f" > /dev/null &

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And then exit the bash shell, I see the following on top

Code:

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PID USERNAME PRI NICE  SIZE  RES STATE    WAIT    TIME    CPU COMMAND
 4372 cd    64    0  164M  146M sleep    biowai  84:25  8.01% grep
 5664 _postfix  2    0  820K  884K sleep    select  86:57  0.00% qmgr

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Now I do the same thing again. Ie

Quote:

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cat < /dev/zero | grep "f" > /dev/null &

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But instead of exiting, I kill the bash session. Which in turn logs me out. When this happens, 2 minutes later, I see

Code:

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  PID USERNAME PRI NICE  SIZE  RES STATE    WAIT    TIME    CPU COMMAND
 4372 cd    -5    0  164M  146M sleep    biowai  84:25  8.01% grep
 5664 _postfix  2    0  820K  884K sleep    select  86:57  0.00% qmgr

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Ie, the PRI changes from 64 to -5 and as a result, the system starts to slow. What would trigger such behavior?

The priority is a dynamic value. You shouldn't expect it to remain the same every time you look at it. It's part of the scheduling algorithm.

Also, I doubt very much that it would affect the performance of the system - it's only using 8% CPU time.

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Mats