On 12/5/19 11:00 AM, [email protected] wrote:
Hi Collen,
Thank you for making this update!
It looks good to me.
One nit:
http://cr.openjdk.java.net/~coleenp/2019/8212160.03/webrev/test/hotspot/jtreg/serviceability/jvmti/CompiledMethodLoad/libCompiledZombie.cpp.html
46 // Continuously generate CompiledMethodLoad events for all
currently compiled methods
47 void JNICALL GenerateEventsThread(jvmtiEnv* jvmti, JNIEnv* jni,
void* arg) {
48 jvmti->SetEventNotificationMode(JVMTI_ENABLE,
JVMTI_EVENT_COMPILED_METHOD_LOAD, NULL);
49 int count = 0;
50
51 while (true) {
52 events = 0;
53 jvmti->GenerateEvents(JVMTI_EVENT_COMPILED_METHOD_LOAD);
54 if (events != 0 && ++count == 200) {
55 printf("Generated %d events\n", events);
56 count = 0;
57 }
58 }
59 }
The above can be simplified a little bit:
if (events % 200 == 199) {
printf("Generated %d events\n", events);
}
Then this line is not needed too:
49 int count = 0;
I answered this too fast. There are two conditions where I want this to
not print. First is where events == 0 and the other for every 200
events that are non-zero.
I could use if (events != 0 && count++ % 200), but I thought what I had
makes more sense and I don't have to worry about when ++ happens.
Thanks,
Coleen
Thanks,
Serguei
On 12/5/19 04:08, [email protected] wrote:
Thanks Dan. I moved the field. For some reason I thought that class
did more/different things than hold per-thread information.
I've retested this version with tiers 2-6.
incr webrev at
http://cr.openjdk.java.net/~coleenp/2019/8212160.03.incr/webrev
full webrev at
http://cr.openjdk.java.net/~coleenp/2019/8212160.03/webrev
Thanks to Serguei for offline discussion.
Coleen
On 12/4/19 7:40 PM, Daniel D. Daugherty wrote:
Generally speaking, JVM/TI related things should be in JvmtiThreadState
instead of directly in the Thread class. That way the extra space is
only
consumed when JVM/TI is in use and only when a Thread does something
that
requires a JvmtiThreadState to be created.
Please reconsider moving _jvmti_event_queue.
Dan
On 12/4/19 6:06 PM, [email protected] wrote:
Hi Serguei,
On 12/4/19 5:15 PM, [email protected] wrote:
Hi Collen, (no problem)
It looks good in general.
Thank you a lot for sorting this out!
Just a couple of comments.
http://cr.openjdk.java.net/~coleenp/2019/8212160.01/webrev/src/hotspot/share/runtime/thread.hpp.frames.html
1993 protected:
1994 // Jvmti Events that cannot be posted in their current context.
1995 // ServiceThread uses this to collect deferred events from
NonJava threads
1996 // that cannot post events.
1997 JvmtiDeferredEventQueue* _jvmti_event_queue;
As David I also have a concern about footprint of having the
_jvmti_event_queue field in the Thread class.
I'm thinking if it'd be better to move this field into the
JvmtiThreadState class.
Please, see jvmti_thread_state() and
JvmtiThreadState::state_for(JavaThread *thread).
The reason I have it directly in JavaThread is so that the GC
oops_do and nmethods_do code can find it easily. I like your idea
of hiding it in jvmti but this doesn't seem good to have this code
know about jvmtiThreadState, which seems to be a queue of Jvmti
states. I also don't want to have jvmtiThreadState to have to add
an oops_do() or nmethods_do() either.
http://cr.openjdk.java.net/~coleenp/2019/8212160.01/webrev/src/hotspot/share/prims/jvmtiImpl.cpp.frames.html
973 void JvmtiDeferredEvent::post(JvmtiEnv* env) {
974 assert(_type == TYPE_COMPILED_METHOD_LOAD, "only user of this
method");
975 nmethod* nm = _event_data.compiled_method_load;
976 JvmtiExport::post_compiled_method_load(env, nm);
977 }
The JvmtiDeferredEvent::post name looks too generic as it posts
compiled load events only.
Do you consider this function extended in the future to support
more event types?
I don't envision an extension for this function but I do for
JvmtiDeferredEventQueue::post(). I have a small enhancement that
would handoff the entire queue to the ServiceThread and have it
call post() to post all the events rather than one at a time.
So I'll rename this one post_compiled_method_load_event() and leave
the other post() as is for now.
open webrev at
http://cr.openjdk.java.net/~coleenp/2019/8212160.02.incr/webrev
Thanks,
Coleen
Thanks,
Serguei
On 11/26/19 06:22, [email protected] wrote:
Summary: Add local deferred event list to thread to post events
outside CodeCache_lock.
This patch builds on the patch for JDK-8173361. With this patch,
I made the JvmtiDeferredEventQueue an instance class (not
AllStatic) and have one per thread. The CodeBlob event that used
to drop the CodeCache_lock and raced with the sweeper thread,
adds the events it wants to post to its thread local list, and
processes it outside the lock. The list is walked in GC and by
the sweeper to keep the nmethods from being unloaded and zombied,
respectively.
Also, the jmethod_id field in nmethod was only used as a boolean
so don't create a jmethod_id until needed for
post_compiled_method_unload.
Ran hs tier1-8 on linux-x64-debug and the stress test that
crashed in the original bug report.
open webrev at
http://cr.openjdk.java.net/~coleenp/2019/8212160.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8212160
Thanks,
Coleen
