[renamed] RFR: 8246135: Save important GC log lines and print them when dumping hs_err files

[stefan.johansson at oracle.com]

Hi Stefan,

On 2020-06-03 10:30, Stefan Karlsson wrote:
> After further deliberations and discussions with Per, Erik and StefanJ, 
> I'm going to make this patch more generic, and split this CR into two 
> parts:
>   JDK-8246135: Save important GC log lines and print them when dumping 
> hs_err files
>   JDK-8246404: ZGC: Use GCLogPrecious for important logging lines
> 
> As StefanJ mentioned earlier there are a separate task for G1, Parallel, 
> and Serial:
>   JDK-8246272: Make use of GCLogPrecious for G1, Parallel and Serial
> 
> Since this patch is becoming more generic than it started out as, I've 
> done some more changes to accommodate that:
>   https://cr.openjdk.java.net/~stefank/8246135/webrev.06
> 
> - Moved the ZGC usages out of this patch
> - Moved initialization out of ZGC so that all GCs can simply start to 
> use this functionality
> - Added a lock to allow for concurrent usage
> - Don't print the GC Precious Log section if the GC isn't using it
> - Added a temp buffer to simplify generation of messages
Looks good!

StefanJ
> 
> The ZGC part has not changed and has already been reviewed:
>   https://cr.openjdk.java.net/~stefank/8246404/webrev.01/
> 
> Some of the stylistic changes in the patch is done to prepare for:
>   https://cr.openjdk.java.net/~stefank/8246405/webrev.01/
> 
> Thanks,
> StefanK
> 
> 
> On 2020-06-02 15:51, Stefan Karlsson wrote:
>> Hi all,
>>
>> While working on getting more information when dumping early during 
>> initialization, it became apparent that we don't print these log lines 
>> as early as we could. In ZGC we can assert and/or fail during the set 
>> up of the heap. I'd like to print the precious lines even when that 
>> happens. The following patch moves the the precious line printing out 
>> of ZCollectedHeap and into a direct call from the VMError code. GCs 
>> that populate these lines will now automatically get them printed.
>>
>> https://cr.openjdk.java.net/~stefank/8246135/webrev.04.delta
>> https://cr.openjdk.java.net/~stefank/8246135/webrev.04
>>
>> Thanks,
>> StefanK
>>
>> On 2020-05-29 12:23, Stefan Karlsson wrote:
>>> Hi all,
>>>
>>> Please review this patch to save some of the important ZGC log lines 
>>> and print them when dumping hs_err files.
>>>
>>> https://cr.openjdk.java.net/~stefank/8246135/webrev.01/
>>> https://bugs.openjdk.java.net/browse/JDK-8246135
>>>
>>> The patch adds a concept of "precious" log lines. What's typically 
>>> logged are GC initialization lines, but also error messages are 
>>> saved. These lines are then dumped in the hs_err file if the JVM 
>>> crashes or hits an assert. The lines can also be printed in a 
>>> debugger to get a quick overview when debugging.
>>>
>>> The precious lines are always saved, but just like any other Unified 
>>> Logging calls, only logged if the tags are enabled.
>>>
>>> The patch builds on the JDK-8246134 patch. The hs_err output looks 
>>> like this:
>>>
>>> ZGC Precious Log:
>>>  NUMA Support: Disabled
>>>  CPUs: 8 total, 8 available
>>>  Memory: 16384M
>>>  Large Page Support: Disabled
>>>  Medium Page Size: 32M
>>>  Workers: 5 parallel, 1 concurrent
>>>  Address Space Type: Contiguous/Unrestricted/Complete
>>>  Address Space Size: 65536M x 3 = 196608M
>>>  Min Capacity: 42M
>>>  Initial Capacity: 256M
>>>  Max Capacity: 4096M
>>>  Max Reserve: 42M
>>>  Pre-touch: Disabled
>>>  Uncommit: Enabled
>>>  Uncommit Delay: 300s
>>>  Runtime Workers: 5 parallel
>>>
>>> ZGC Globals:
>>>  GlobalPhase:       2 (Relocate)
>>>  GlobalSeqNum:      1
>>>  Offset Max:        4096G (0x0000040000000000)
>>>  Page Size Small:   2M
>>>  Page Size Medium:  32M
>>>
>>> ZGC Metadata Bits:
>>>  Good:              0x0000100000000000
>>>  Bad:               0x00002c0000000000
>>>  WeakBad:           0x00000c0000000000
>>>  Marked:            0x0000040000000000
>>>  Remapped:          0x0000100000000000
>>>
>>> Heap:
>>>  ZHeap           used 12M, capacity 256M, max capacity 4096M
>>>  Metaspace       used 6501K, capacity 6615K, committed 6784K, 
>>> reserved 1056768K
>>>   class space    used 559K, capacity 588K, committed 640K, reserved 
>>> 1048576K
>>>
>>> ZGC Page Table:
>>>  Small   0x0000000000000000 0x0000000000200000 0x0000000000200000 
>>> Allocating
>>>  Small   0x0000000000200000 0x0000000000240000 0x0000000000400000 
>>> Allocating
>>>  Small   0x0000000000400000 0x0000000000600000 0x0000000000600000 
>>> Allocating
>>>  Small   0x0000000000600000 0x0000000000800000 0x0000000000800000 
>>> Allocating
>>>  Small   0x0000000000800000 0x00000000009c0000 0x0000000000a00000 
>>> Allocating
>>>  Small   0x0000000000a00000 0x0000000000a40000 0x0000000000c00000 
>>> Allocating
>>>
>>> Thanks,
>>> StefanK
>>
>