1430188 - {i,}wt_matrix_ref tables in libaom are enormous and not read-only

Status: RESOLVED FIXED

(Core :: Audio/Video, enhancement)

Description

[Nathan Froyd [:froydnj]]

Noticed this while looking at sizes of libxul symbols for something else today:

0x34400 OBJECT  LOCAL  DEFAULT   28 iwt_matrix_ref
0x34400 OBJECT  LOCAL  DEFAULT   28 wt_matrix_ref

That is, both of these tables are ~200KB, and they are stored in the writable data section.  They are initialized in the source code, so I think the intent is that they're read-only, but since they're lacking the `const` qualifier, they are unsharable between processes.  Thus we have ~400KB of private data in each process that really shouldn't be there.

I can't tell whether they're actually writable or not; it looks like they shouldn't be, but AFAICT the sole references are from unused functions (?).

Ralph, can you look into this and/or get this fixed upstream?  Upstream at least looks like they're still writable:

https://aomedia.googlesource.com/aom/+/master/av1/common/quant_common.c#582
https://aomedia.googlesource.com/aom/+/master/av1/common/quant_common.c#7350

Comment 1

[Ralph Giles (:rillian)]

Thanks for the report. Patch submitted as https://aomedia-review.googlesource.com/#/c/aom/+/41822

Comment 2

[Nathan Froyd [:froydnj]]

Thank you!

Comment 3

[Ralph Giles (:rillian)]

Attachment: Bug 1430188: av1: Mark AOM_QM matricies const. .

These large (200 KB) static stables are functionally read-only.
Marking them const moves them to the read-only section of shared
libraries, reducing memory footprint when multiple application
processes are running simultaneously.

This is a backport of the upstream commit 90243cf9e670.

Review commit: https://reviewboard.mozilla.org/r/212980/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/212980/

Comment 4

[Matthew Gregan [:kinetik]]

Comment on attachment 8942711 [details]
Bug 1430188: av1: Mark AOM_QM matricies const. .

https://reviewboard.mozilla.org/r/212980/#review218644

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d88cb52f392d
av1: Mark AOM_QM matricies const. r=kinetik.

Comment 6

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/d88cb52f392d