Tornado

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Browser
Figure 6-23
Fragmented Memory as Seen in the Browser
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6.12.4 Priority Inversion
The browser’s displays are most useful when they complement each other. For
example, suppose you notice in the main browser window (as in Figure 6-24) that
a task expected to be high priority is blocked while two other tasks are ready to
run.
An immediate thing to check is whether the three tasks really have the expected
priority relationship (in this example, the names are chosen to suggest the
intended priorities: uHi is supposed to have highest priority, uMed medium
priority, and uLow the lowest). You can check this immediately by clicking on each
task’s summary line, thus bringing up the windows shown in Figure 6-25.
Unfortunately, that turns out not to be the explanation; the priorities (shown for
each task under Attributes) are indeed as expected. Examining the CPU allocations
with the spy window (Figure 6-26) reveals that the observed situation is ongoing;
uMed is monopolizing the target CPU. It should certainly execute by preference to
the low-priority uLow, but why is uHi not getting to run?
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