RFR: 8246135: ZGC: Save important log lines and print them when dumping hs_err files

[Erik Österlund]

Hi Stefan,

Looks good.

Thanks,
/Erik

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