Hi,
I am trying to figure out how to reduce the performance impact of dtrace when
run with java probes. Currently the script that i am running seems to
significantly impact the performance of my java web app.
I've been trying to use the profile:::profile-1001hz probe to reduce the
resolution of events processed by dtrace but have had no success (I'm probably
not using it correctly).
Here is my script, any ideas how I can reduce the overhead? I am happy to
reduce the resolution of events that are processed if there is a way to do
that, or anything else anyone can think of.
thanks.
#!/usr/sbin/dtrace -CZs
self long start;
self short in_lock;
string package_s;
string package_e;
BEGIN
{
package_s = "com/foo/aaa";
package_e = "com/foo/zzz";
start = timestamp;
}
/*
* hotspot:::method-entry, hotspot:::method-return probe arguments:
* arg0: uintptr_t, Java thread id
* arg1: char*, a pointer to mUTF-8 string containing the name of
* the class of the method being entered
* arg2: uintptr_t, the length of the class name (in bytes)
* arg3: char*, a pointer to mUTF-8 string data which contains the
* name of the method being entered
* arg4: uintptr_t, the length of the method name (in bytes)
* arg5: char*, a pointer to mUTF-8 string data which contains the
* signature of the method being entered
* arg6: uintptr_t, the length of the signature(in bytes)
*/
hotspot$target:::method-return
/self->start && (copyin(arg1, arg2+1) >= package_s && copyin(arg1, arg2+1) <=
package_e)/
{
self->str_ptr = (char*) copyin(arg3, arg4+1);
self->str_ptr[arg4] = '\0';
self->method_name = (string) self->str_ptr;
self->str_ptr = (char*) copyin(arg1, arg2+1);
self->str_ptr[arg2] = '\0';
self->class_name = (string) self->str_ptr;
@method_time[self->class_name, self->method_name] = sum((timestamp -
self->start) / 1000000);
self->start = NULL;
}
hotspot$target:::method-entry
/(copyin(arg1, arg2+1) >= package_s && copyin(arg1, arg2+1) <= package_e)/
{
self->start = timestamp;
self->str_ptr = (char*) copyin(arg1, arg2+1);
self->str_ptr[arg2] = '\0';
self->class_name = (string) self->str_ptr;
self->str_ptr = (char*) copyin(arg3, arg4+1);
self->str_ptr[arg4] = '\0';
self->method_name = (string) self->str_ptr;
self->str_ptr = (char*) copyin(arg5, arg6+1);
self->str_ptr[arg6] = '\0';
self->signature = (string) self->str_ptr;
@method_count[self->class_name, self->method_name] = count();
}
END
{
printf("\nCOUNT\n======================\n");
printa(@method_count);
printf("\nTIME\n======================\n");
printa(@method_time);
exit(0);
}
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