Tool Where to

Find It

What It Does

truss /usr/bin The SVr4 version of trace. This tool prints out the system calls that an

executable makes. Use it to see what a binary is doing, and why it's stuck

or failing. This is a great help!

ps /usr/bin Displays process characteristics.

ctrace Comes with

compiler

Modifies your source to print lines as they are executed. A great tool for

small programs!

debugger Comes with

compiler

Interactive debugger.

file /usr/bin Tells you what a file contains (e.g., executable, data, ASCII, shell script,

archive, etc.).

Table 6-4. Tools to Help with Performance Tuning

Tool Where to Find

It

What It Does

collector Comes with

debugger

(SunOS only) Collects runtime performance data under the control

of the debugger.

analyzer Comes with

debugger

(SunOS only) Analyzes collected performance data.

gprof /usr/ccs/bin Displays the call-graph profile data (identifies the compute-

intensive functions).

prof /usr/ccs/bin Displays the percentage of time spent in each routi ne.

tcov Comes with

compiler

Displays a count of how often each statement is executed (identifies

the compute-intensive loops within a function).

time /usr/bin/time Displays the total real and CPU time used by a program.

If you're working on the OS kernel, most of the runtime tools are not available to you, because the
kernel does not run as a user process. The compiletime tools, like lint, work, but otherwise we have to
use the stone knives and flint axes: putting nonrandom patterns in memory to see when they are

overwritten (two favorites are the hex constants dead-beef and abadcafe), using printf 's or

their equivalent, and logging trace information.

Software Dogma

Debugging the Ker nel with grep

A kernel "panics", or comes to an abrupt halt, when it detects a situation that "cannot" arise.
For example, it finds a null pointer when looking for some essential data. Since there is no
way it can recover from this, the safest course is to halt the processor before more data
disappears. To solve a panic, you must first consider what happened that could possibly