Often a D program is easier to read if you break up a complex predicate
into separate clauses, but I was wondering if you sacrifice script
performance to do that. For example, the following two D programs do
the same thing (Do a 20 second interval quantize of pread/pwrite block
sizes for a specific Oracle DB instance). Clearly "ora1.d" is easier to
read, but is "ora2.d" more efficient?
# cat ora1.d
#!/usr/sbin/dtrace -s
/*
Quantize IO blocksize for Oracle random I/O
for specific DB instance.
*/
#pragma D option quiet
inline string parmDBinst = $$1;
syscall::pread*:entry,
syscall::pwrite*:entry
/ execname == "oracle" /
{
this->cmd = strtok(curpsinfo->pr_psargs, " ");
this->dbinst =
(substr(this->cmd,0,6) == "oracle") ? substr(this->cmd,6) :
(substr(this->cmd,0,4) == "ora_" ? substr(this->cmd,9) :
"noDBnoDB");
}
syscall::pread*:entry,
syscall::pwrite*:entry
/ this->dbinst == parmDBinst /
{
@IO[probefunc] = quantize(arg2);
}
tick-20s,END
{
printf ("%Y\n", walltimestamp);
printa (@IO);
clear (@IO);
}
# cat ora2.d
#!/usr/sbin/dtrace -s
/*
Quantize IO blocksize for Oracle random I/O
for specific DB instance.
*/
#pragma D option quiet
inline string parmDBinst = $$1;
syscall::pread*:entry,
syscall::pwrite*:entry
/ execname == "oracle" &&
(this->cmd = strtok(curpsinfo->pr_psargs, " "),
parmDBinst == ((substr(this->cmd,0,6) == "oracle") ?
substr(this->cmd,6) :
(substr(this->cmd,0,4) == "ora_" ? substr(this->cmd,9) :
"noDBnoDB"))) /
{
@IO[probefunc] = quantize(arg2);
}
tick-20s,END
{
printf ("%Y\n", walltimestamp);
printa (@IO);
clear (@IO);
}
#
Thanks,
Chip Bennett
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