From shade at openjdk.java.net  Tue Mar  8 09:45:30 2022
From: shade at openjdk.java.net (Aleksey Shipilev)
Date: Tue, 8 Mar 2022 09:45:30 GMT
Subject: RFR: CODETOOLS-7903119: JOL: Experimental support for Lilliput
Message-ID: <wT3607d6TpJRGU69nBXy1pzHFU5duCySDGM2spIQjLY=.418090fb-af55-43ef-8e4a-c35a4fd77e66@github.com>

Project Lilliput aims to reduce the size of the object header. JOL can support that project by detecting the Lilliput VM and printing out object internals more precisely. 

Sample output on JDK 19+:


# Running 64-bit HotSpot VM.
# Using compressed oop with 3-bit shift.
# Using compressed klass with 3-bit shift.
# Objects are 8 bytes aligned.
#                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
# Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
# Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
# Array base offsets:    16,   16,   16,   16,   16,   16,   16,   16,   16

[B object internals:
OFF  SZ   TYPE DESCRIPTION               VALUE
  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)
  8   4        (object header: class)    0x00001ea0
 12   4        (array length)            5
 16   5   byte [B.<elements>             N/A
 21   3        (object alignment gap)    
Instance size: 24 bytes
Space losses: 0 bytes internal + 3 bytes external = 3 bytes total


Sample output on current Lilliput:


# Running 64-bit HotSpot VM.
# Lilliput VM detected (experimental).
# Using compressed oop with 3-bit shift.
# Using compressed klass with 3-bit shift.
# Objects are 8 bytes aligned.
#                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
# Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
# Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
# Array base offsets:    16,   16,   16,   16,   16,   16,   16,   16,   16

[B object internals:
OFF  SZ   TYPE DESCRIPTION               VALUE
  0   8        (object header: mark)     0x0000001200000001 (Lilliput)
  8   4        (array length)            4
 12   4        (alignment/padding gap)   
 16   4   byte [B.<elements>             N/A
 20   4        (object alignment gap)    
Instance size: 24 bytes
Space losses: 4 bytes internal + 4 bytes external = 8 bytes total


Sample run on Lilliput + https://github.com/openjdk/lilliput/pull/41:


# Running 64-bit HotSpot VM.
# Lilliput VM detected (experimental).
# Using compressed oop with 3-bit shift.
# Using compressed klass with 3-bit shift.
# Objects are 8 bytes aligned.
#                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
# Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
# Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
# Array base offsets:    12,   12,   12,   12,   12,   12,   12,   16,   16

[B object internals:
OFF  SZ   TYPE DESCRIPTION               VALUE
  0   8        (object header: mark)     0x0000001200000001 (Lilliput)
  8   4        (array length)            4
 12   4   byte [B.<elements>             N/A
Instance size: 16 bytes
Space losses: 0 bytes internal + 0 bytes external = 0 bytes total

-------------

Commit messages:
 - Support Lilliput

Changes: https://git.openjdk.java.net/jol/pull/22/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jol&pr=22&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903119
  Stats: 73 lines in 3 files changed: 66 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/jol/pull/22.diff
  Fetch: git fetch https://git.openjdk.java.net/jol pull/22/head:pull/22

PR: https://git.openjdk.java.net/jol/pull/22

From shade at openjdk.java.net  Tue Mar  8 10:17:54 2022
From: shade at openjdk.java.net (Aleksey Shipilev)
Date: Tue, 8 Mar 2022 10:17:54 GMT
Subject: RFR: CODETOOLS-7903119: JOL: Experimental support for Lilliput
 [v2]
In-Reply-To: <wT3607d6TpJRGU69nBXy1pzHFU5duCySDGM2spIQjLY=.418090fb-af55-43ef-8e4a-c35a4fd77e66@github.com>
References: <wT3607d6TpJRGU69nBXy1pzHFU5duCySDGM2spIQjLY=.418090fb-af55-43ef-8e4a-c35a4fd77e66@github.com>
Message-ID: <zop-7MmB2mLW2sCk6k2dZr_QyP_oJtH8kXMpMzCUnKU=.d73b3b2e-d4a4-40ea-b99f-9ac990332d07@github.com>

> Project Lilliput aims to reduce the size of the object header. JOL can support that project by detecting the Lilliput VM and printing out object internals more precisely. 
> 
> Sample output on JDK 19+:
> 
> 
> # Running 64-bit HotSpot VM.
> # Using compressed oop with 3-bit shift.
> # Using compressed klass with 3-bit shift.
> # Objects are 8 bytes aligned.
> #                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
> # Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array base offsets:    16,   16,   16,   16,   16,   16,   16,   16,   16
> 
> [B object internals:
> OFF  SZ   TYPE DESCRIPTION               VALUE
>   0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)
>   8   4        (object header: class)    0x00001ea0
>  12   4        (array length)            5
>  16   5   byte [B.<elements>             N/A
>  21   3        (object alignment gap)    
> Instance size: 24 bytes
> Space losses: 0 bytes internal + 3 bytes external = 3 bytes total
> 
> 
> Sample output on current Lilliput:
> 
> 
> # Running 64-bit HotSpot VM.
> # Lilliput VM detected (experimental).
> # Using compressed oop with 3-bit shift.
> # Using compressed klass with 3-bit shift.
> # Objects are 8 bytes aligned.
> #                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
> # Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array base offsets:    16,   16,   16,   16,   16,   16,   16,   16,   16
> 
> [B object internals:
> OFF  SZ   TYPE DESCRIPTION               VALUE
>   0   8        (object header: mark)     0x0000001200000001 (Lilliput)
>   8   4        (array length)            4
>  12   4        (alignment/padding gap)   
>  16   4   byte [B.<elements>             N/A
>  20   4        (object alignment gap)    
> Instance size: 24 bytes
> Space losses: 4 bytes internal + 4 bytes external = 8 bytes total
> 
> 
> Sample run on Lilliput + https://github.com/openjdk/lilliput/pull/41:
> 
> 
> # Running 64-bit HotSpot VM.
> # Lilliput VM detected (experimental).
> # Using compressed oop with 3-bit shift.
> # Using compressed klass with 3-bit shift.
> # Objects are 8 bytes aligned.
> #                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
> # Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array base offsets:    12,   12,   12,   12,   12,   12,   12,   16,   16
> 
> [B object internals:
> OFF  SZ   TYPE DESCRIPTION               VALUE
>   0   8        (object header: mark)     0x0000001200000001 (Lilliput)
>   8   4        (array length)            4
>  12   4   byte [B.<elements>             N/A
> Instance size: 16 bytes
> Space losses: 0 bytes internal + 0 bytes external = 0 bytes total

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Much more reliable detection scheme

-------------

Changes:
  - all: https://git.openjdk.java.net/jol/pull/22/files
  - new: https://git.openjdk.java.net/jol/pull/22/files/b7fde914..0052a7b2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jol&pr=22&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jol&pr=22&range=00-01

  Stats: 23 lines in 1 file changed: 13 ins; 2 del; 8 mod
  Patch: https://git.openjdk.java.net/jol/pull/22.diff
  Fetch: git fetch https://git.openjdk.java.net/jol pull/22/head:pull/22

PR: https://git.openjdk.java.net/jol/pull/22

From duke at openjdk.java.net  Tue Mar  8 17:47:15 2022
From: duke at openjdk.java.net (duke)
Date: Tue, 8 Mar 2022 17:47:15 GMT
Subject: git: openjdk/jol: 7903119: JOL: Experimental support for Lilliput
Message-ID: <d27b4b2e-8156-4dcf-9cb6-3c9f4911b176@openjdk.java.net>

Changeset: affdda22
Author:    Aleksey Shipil?v <shade at redhat.com>
Committer: GitHub <noreply at github.com>
Date:      2022-03-08 18:45:28 +0000
URL:       https://git.openjdk.java.net/jol/commit/affdda229185a73385155a7479f7e348e854558b

7903119: JOL: Experimental support for Lilliput


! jol-core/src/main/java/org/openjdk/jol/info/ClassLayout.java
! jol-core/src/main/java/org/openjdk/jol/vm/Experiments.java
! jol-core/src/main/java/org/openjdk/jol/vm/HotspotUnsafe.java


From shade at openjdk.java.net  Tue Mar  8 17:48:29 2022
From: shade at openjdk.java.net (Aleksey Shipilev)
Date: Tue, 8 Mar 2022 17:48:29 GMT
Subject: Withdrawn: CODETOOLS-7903119: JOL: Experimental support for Lilliput
In-Reply-To: <wT3607d6TpJRGU69nBXy1pzHFU5duCySDGM2spIQjLY=.418090fb-af55-43ef-8e4a-c35a4fd77e66@github.com>
References: <wT3607d6TpJRGU69nBXy1pzHFU5duCySDGM2spIQjLY=.418090fb-af55-43ef-8e4a-c35a4fd77e66@github.com>
Message-ID: <jhTpFStRMm73fg7Dcnr6WujRQY2GB1iOAN81IkCjlGk=.10fce64b-cef1-4bc0-aba7-df5ad33acd27@github.com>

On Tue, 8 Mar 2022 09:40:18 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Project Lilliput aims to reduce the size of the object header. JOL can support that project by detecting the Lilliput VM and printing out object internals more precisely. 
> 
> Sample output on JDK 19+:
> 
> 
> # Running 64-bit HotSpot VM.
> # Using compressed oop with 3-bit shift.
> # Using compressed klass with 3-bit shift.
> # Objects are 8 bytes aligned.
> #                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
> # Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array base offsets:    16,   16,   16,   16,   16,   16,   16,   16,   16
> 
> [B object internals:
> OFF  SZ   TYPE DESCRIPTION               VALUE
>   0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)
>   8   4        (object header: class)    0x00001ea0
>  12   4        (array length)            5
>  16   5   byte [B.<elements>             N/A
>  21   3        (object alignment gap)    
> Instance size: 24 bytes
> Space losses: 0 bytes internal + 3 bytes external = 3 bytes total
> 
> 
> Sample output on current Lilliput:
> 
> 
> # Running 64-bit HotSpot VM.
> # Lilliput VM detected (experimental).
> # Using compressed oop with 3-bit shift.
> # Using compressed klass with 3-bit shift.
> # Objects are 8 bytes aligned.
> #                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
> # Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array base offsets:    16,   16,   16,   16,   16,   16,   16,   16,   16
> 
> [B object internals:
> OFF  SZ   TYPE DESCRIPTION               VALUE
>   0   8        (object header: mark)     0x0000001200000001 (Lilliput)
>   8   4        (array length)            4
>  12   4        (alignment/padding gap)   
>  16   4   byte [B.<elements>             N/A
>  20   4        (object alignment gap)    
> Instance size: 24 bytes
> Space losses: 4 bytes internal + 4 bytes external = 8 bytes total
> 
> 
> Sample run on Lilliput + https://github.com/openjdk/lilliput/pull/41:
> 
> 
> # Running 64-bit HotSpot VM.
> # Lilliput VM detected (experimental).
> # Using compressed oop with 3-bit shift.
> # Using compressed klass with 3-bit shift.
> # Objects are 8 bytes aligned.
> #                       ref, bool, byte, char, shrt,  int,  flt,  lng,  dbl
> # Field sizes:            4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array element sizes:    4,    1,    1,    2,    2,    4,    4,    8,    8
> # Array base offsets:    12,   12,   12,   12,   12,   12,   12,   16,   16
> 
> [B object internals:
> OFF  SZ   TYPE DESCRIPTION               VALUE
>   0   8        (object header: mark)     0x0000001200000001 (Lilliput)
>   8   4        (array length)            4
>  12   4   byte [B.<elements>             N/A
> Instance size: 16 bytes
> Space losses: 0 bytes internal + 0 bytes external = 0 bytes total

This pull request has been closed without being integrated.

-------------

PR: https://git.openjdk.java.net/jol/pull/22