8222670 patch review: prevent downgraded tasks from recompiling

[Liu, Xin]

Hi, Tobias, 
Here is the new revision of webrev. It includes the tieredEvent you mentioned. 	
https://cr.openjdk.java.net/~xliu/8222670/webrev.05/

Paul help me to try the patch in submit repo. It's clean. 

Thanks,
--lx


From: "do-not-reply at oracle.com" <do-not-reply at oracle.com>
Reply-To: "mach5_admin_ww_grp at oracle.com" <mach5_admin_ww_grp at oracle.com>
Date: Monday, May 6, 2019 at 11:25 AM
To: "Hohensee, Paul" <hohensee at amazon.com>
Subject: [Mach5] mach5-one-phh-JDK-8222670-1-20190506-1730-2299657: PASSED
 
Job: mach5-one-phh-JDK-8222670-1-20190506-1730-2299657

BuildId: 2019-05-06-1725217.hohensee.source

No failed tests

Tasks Summary

NA: 0
UNABLE_TO_RUN: 0
PASSED: 76
HARNESS_ERROR: 0
EXECUTED_WITH_FAILURE: 0
KILLED: 0
FAILED: 0
NOTHING_TO_RUN: 0



On 5/3/19, 5:30 AM, "Tobias Hartmann" <tobias.hartmann at oracle.com> wrote:

    
    On 03.05.19 02:21, Liu, Xin wrote:
    > Thanks for the review. I fixed copyrights and  the typo of clearMethodState0.
    > Here is the new revision. 
    > https://cr.openjdk.java.net/~xliu/8222670/webrev.04/
    
    Looks good to me but I think you should also add:
    
    if (PrintTieredEvents) {
      print_event(REMOVE_FROM_QUEUE, method, method, task->osr_bci(), (CompLevel) task->comp_level());
    }
    
    >     But why is that? If a downgraded compilation succeeded at level 2, shouldn't a re-compilation at the
    >     same level be detected by CompileBroker::compilation_is_complete() in CompileBroker::compile_method()?
    >     
    > That's the very root cause of level2 recompilation. 
    > In CompileBroker::compile_method(), its input argument is comp_level = 3. 
    > CompileBroker::compilation_is_complete returns false because codecache only has level=2 nmethod. 
    > I don't know why, but hotpsot is also very stubborn.  It will request level = 3 again and again.  All of them are downgraded to level=2 when they dequeue. 
    > 
    > Level2RecompilationTest simulates this process. I didn't make it up. I observe the symptom in some real services as follows. 
    > https://bugs.openjdk.java.net/secure/attachment/82079/lvl2_recomp_spring.log.zip 
    
    Okay, got it.
    
    Thanks,
    Tobias