1665258 - Shrink some structs by reordering fields

Status: RESOLVED FIXED

(Core :: General, task)

Description

[Nicholas Nethercote [inactive]]

I looked through the "excessive padding" reports in a firefox-scan-build run. Most of them weren't interesting, involving structs like JSRuntime that are very large (so the proportion of wasted space is small) and/or instantiated a small number of times.

But there were three ones worth fixing for some tiny wins.

Comment 1

[Nicholas Nethercote [inactive]]

Attachment: Bug 1665258 - Shrink `CSSEquivTable`. r=heycam

Better field packing reduces it from 48 bytes to 40 bytes on 64-bit.

This reduces the memory used by each process by 336 bytes on 64-bit.

Comment 2

[Nicholas Nethercote [inactive]]

Attachment: Bug 1665258 - Shrink `HistogramInfo`. r=chutten

Better field packing reduces it from 48 bytes to 44 bytes on 64-bit.

This reduces the size of the text section by 14,288 bytes, due to
gHistogramInfos shrinking.

Depends on D90344

Comment 3

[Nicholas Nethercote [inactive]]

Attachment: Bug 1665258 - Shrink SpoofingKeyboardInfo. r=timhuang

This reduces the size of spoofingKeyboardInfoTable from 4 KiB to 3 KiB,
saving of memory 1 KiB per process.

Depends on D90345

Comment 4

[Sylvestre Ledru [:Sylvestre]]

thanks!

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c8657e9dd191
Shrink `CSSEquivTable`. r=heycam
https://hg.mozilla.org/integration/autoland/rev/b21c1c12747d
Shrink `HistogramInfo`. r=chutten
https://hg.mozilla.org/integration/autoland/rev/1f949d96cddd
Shrink SpoofingKeyboardInfo. r=timhuang

Comment 6

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/c8657e9dd191
https://hg.mozilla.org/mozilla-central/rev/b21c1c12747d
https://hg.mozilla.org/mozilla-central/rev/1f949d96cddd