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odeke-em opened this issue Nov 6, 2020 · 6 comments · Fixed by #24
Closed

detect when rearrangement changes the size class #22

odeke-em opened this issue Nov 6, 2020 · 6 comments · Fixed by #24
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enhancement New feature or request

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@odeke-em
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odeke-em commented Nov 6, 2020

Coming here from a suggestion from Josh Bleecher Snyder, we should detect when the rearrangement changes the size class of the struct.
@odeke-em odeke-em added the enhancement New feature or request label Nov 6, 2020
@cuonglm
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cuonglm commented Nov 6, 2020

@odeke-em do you refer to the size class that runtime use to allocate memory for struct? https://golang.org/src/runtime/mksizeclasses.go

@odeke-em
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odeke-em commented Nov 6, 2020

That's right! Please see also see golang/go#42412 (comment)

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cuonglm commented Nov 6, 2020

Look cool!

So when size class changed, what should we report? Or we will report the actual size class instead of the struct size?

@odeke-em
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odeke-em commented Nov 6, 2020

We should report all of them. Basically:

<LINENO_POS>: struct has size 112 (size class <CLASS_SIZE>), rearrange to <REARRANGEMENT> for optimal size

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odeke-em commented Nov 6, 2020

Also we should make sure that the optimal size suggested is an actual size class.

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odeke-em commented Nov 6, 2020

For brevity here are the size classes from the Go runtime https://github.com/golang/go/blob/ecc3f5112ebaf23c4b1ac4c5eedfa406d82ecc9a/src/runtime/sizeclasses.go#L6-L73

@odeke-em odeke-em mentioned this issue Nov 6, 2020
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cuonglm pushed a commit that referenced this issue Nov 6, 2020
@cuonglm
Use runtime actual size class for checking sloppy
5b3e7a8 
The runtime use diferrent size class to allocate memory. So a struct
with size 32 and size 24 are atually consume the same amount of memory,
size class 32. So they're not sloppy.

Instead, we only report if the rearrangement makes actual change in
runtime size class.

Fixes #22
@cuonglm cuonglm mentioned this issue Nov 6, 2020
Merged
cuonglm pushed a commit that referenced this issue Nov 6, 2020
@cuonglm
Use runtime actual size class for checking sloppy
4faefc9 
The runtime use diferrent size class to allocate memory. So a struct
with size 32 and size 24 are atually consume the same amount of memory,
size class 32. So they're not sloppy.

Instead, we only report if the rearrangement makes actual change in
runtime size class.

Fixes #22
cuonglm pushed a commit that referenced this issue Nov 6, 2020
@cuonglm
Use runtime actual size class for checking sloppy
046a264 
The runtime use diferrent size class to allocate memory. So a struct
with size 32 and size 24 are atually consume the same amount of memory,
size class 32. So they're not sloppy.

Instead, we only report if the rearrangement makes actual change in
runtime size class.

Fixes #22
cuonglm pushed a commit that referenced this issue Nov 6, 2020
@cuonglm
Use runtime actual size class for checking sloppy
8107852 
The runtime use diferrent size class to allocate memory. So a struct
with size 32 and size 24 are atually consume the same amount of memory,
size class 32. So they're not sloppy.

Instead, we only report if the rearrangement makes actual change in
runtime size class.

Fixes #22
cuonglm pushed a commit that referenced this issue Nov 6, 2020
@cuonglm
Running CI with go tip
84ea3e3 
Since when we use "go:linkname", we should always run CI with tip to see
if it's broken or not.

Updates #22
@cuonglm cuonglm mentioned this issue Nov 6, 2020
Merged
cuonglm pushed a commit that referenced this issue Nov 6, 2020
@cuonglm
Running CI with go tip
f71694b 
Since when we use "go:linkname", we should always run CI with tip to see
if it's broken or not.

Updates #22
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Use runtime actual size class for checking sloppy orijtech/structslop
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@cuonglm @odeke-em