Bug: ZGC does not support NMT

Per Liden per.liden at oracle.com
Mon Dec 11 09:39:47 UTC 2017


We haven't added support for that yet. ZGC is not using the normal 
os::reserve/commit_memory paths for the heap memory so we don't get that 
"for free", as other GCs do.

/Per

On 2017-12-11 10:00, Aleksey Shipilev wrote:
> Trying to run ZGC with NMT support, and there is no "Java Heap" section. I guess mtJavaHeap tag is
> missing in heap allocation code within ZGC.
>
> $ java -XX:+UseZGC -Xms8g -Xmx8g -XX:NativeMemoryTracking=summary Hello
>
> $ jcmd 57529 VM.native_memory
>
> Total: reserved=310485KB, committed=66769KB
> -                     Class (reserved=8303KB, committed=4463KB)
>                             (classes #461)
>                             (malloc=111KB #603)
>                             (mmap: reserved=8192KB, committed=4352KB)
>                             (  Metadata:   )
>                             (    reserved=8192KB, committed=4352KB)
>                             (    used=3703KB)
>                             (    free=649KB)
>                             (    waste=0KB =0.00%)
>
> -                    Thread (reserved=34978KB, committed=34978KB)
>                             (thread #35)
>                             (stack: reserved=34892KB, committed=34892KB)
>                             (malloc=47KB #187)
>                             (arena=40KB #56)
>
> -                      Code (reserved=247726KB, committed=7850KB)
>                             (malloc=42KB #474)
>                             (mmap: reserved=247684KB, committed=7808KB)
>
> -                        GC (reserved=16921KB, committed=16921KB)
>                             (malloc=537KB #51)
>                             (mmap: reserved=16384KB, committed=16384KB)
>
> -                  Compiler (reserved=149KB, committed=149KB)
>                             (malloc=18KB #53)
>                             (arena=131KB #15)
>
> -                  Internal (reserved=317KB, committed=317KB)
>                             (malloc=285KB #1058)
>                             (mmap: reserved=32KB, committed=32KB)
>
> -                    Symbol (reserved=1727KB, committed=1727KB)
>                             (malloc=1111KB #1051)
>                             (arena=616KB #1)
>
> -    Native Memory Tracking (reserved=89KB, committed=89KB)
>                             (malloc=5KB #56)
>                             (tracking overhead=84KB)
>
> -               Arena Chunk (reserved=185KB, committed=185KB)
>                             (malloc=185KB)
>
> -                   Logging (reserved=8KB, committed=8KB)
>                             (malloc=8KB #158)
>
> -                 Arguments (reserved=17KB, committed=17KB)
>                             (malloc=17KB #463)
>
> -                    Module (reserved=57KB, committed=57KB)
>                             (malloc=57KB #1129)
>
> -                   Unknown (reserved=8KB, committed=8KB)
>                             (mmap: reserved=8KB, committed=8KB)
>
> Thanks,
> -Aleksey
>


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