For each problem, the three questions shown in Figure 1-4 must be answered:
Where is time spent? First, you have to identify where time goes. For example, if a specific
operation takes ten seconds, you have to find out which module or component most of
these ten seconds are used up in.
How is time spent? Once you know where the time goes, you have to find out how that time
is spent. For example, you may find out that the application spends 4.2 seconds on CPU,
0.4 seconds doing I/O operations, and 5.1 seconds waiting for dequeuing a message coming
from another component.
How can time spent be reduced? Finally, it is time to find out how the operation can be made
faster. To do so, it is essential to focus on the most time-consuming part of the processing.
For example, if I/O operations take 4 percent of the overall processing time, it makes no
sense to start tuning them, even if they are very slow.
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