Hello!
I need to measure the time spent in one process, and I need to do
it as exact as possible (about 1us). 2.2.x kernel series, Pentium II
proc.
My first and not-yet-working solution:
I declared 3 variables in the arch/i386/kernel/process.c:
static pid_t ProcID;
static unsigned long long int RunStart;
static unsigned long long int Elapsed;
ProcID is the process id, which needs to be profiled. Elapsed is
the time commulated in the process running, RunStart is a temporary
variable.
I put some additional code to the beginning of the __switch_to in
the arch/i386/kernel/process.c:
if (prev->pid == ProcID) {
Elapsed += rdtsc_return()-RunStart;
} else if (next->pid == ProcID) {
RunStart = rdtsc_return();
};
rdtsc_return() is a function, which returns the Pentium clock in
long long int format.
These code checks if the process we want to measure is on the
schedule or not.
After it I wanted to write a kernel module, which registered a
file in the /proc, and it can set the ProcID via it, and get the
"Elapsed" value from it.
The problem is that I don't know how I use that variables.
I tried this:
extern pid_t ProcID;
extern long long int Elapsed;
But when I want to use my module, it prints:
or2:/projects/boomerang/timer# insmod timermod.o
timermod.o: unresolved symbol ProcID
timermod.o: unresolved symbol Elapsed
(The timermod.c originally based on the procfs.c file, which is
included in some kernel howto.)
The System.map file in the /usr/src/linux-2.2.13 contains that
symbols:
c021c8c0 b ProcID
c021c8cc b Elapsed
I copied the System.map into /boot/System.map-2.2.13,
/lib/modules/2.2.13, but it doesn't help. Do you know how I can
access those variables?
Another question:
-----------------
Do you know a better and faster way to access that variables? May I
make a device driver for it? Make a syscall? Please refer me to the
URL when I can study these materials.
Thanks for any help in advance,
dLux
--
God save the screen!
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