1032656 - bzero hang in OfflineAudioContext constructor

Status: RESOLVED FIXED

(Core :: Web Audio, defect)

Description

[Jesse Ruderman]

Attachment: testcase

In a debug build or ASan build, this hangs for 5+ seconds. In a nightly build, it doesn't. Weird. What do debug and ASan builds have in common?

Comment 1

[Jesse Ruderman]

Attachment: sample-asan.txt

Comment 2

[Jesse Ruderman]

Attachment: sample-debug.txt

Comment 3

[Paul Adenot (:padenot)]

Attachment: Allocate the output buffer for OfflineAudioContext off-main-thread. r=

ASAN and debug build zero memory when allocating, I believe. Release build
don't. And ASAN should have some allocation overhead on top of that.

This test case allocates a 16GB buffer, and zeroing it takes some time.
Nevertheless, we can make it better by allocating the output buffer lazily on
the rendering thread instead of doing it on the main thread. Because Jesse's
testcase does not call `startRendering`, no memory is even allocated anymore.

Comment 4

[(no longer active)]

Comment on attachment 8510289 [details] [diff] [review]
Allocate the output buffer for OfflineAudioContext off-main-thread. r=

Review of attachment 8510289 [details] [diff] [review]:
-----------------------------------------------------------------

::: content/media/webaudio/AudioDestinationNode.cpp
@@ +184,4 @@
>    // How many frames the OfflineAudioContext intends to produce.
>    uint32_t mLength;
>    float mSampleRate;
> +  bool mBufferAllocated;

A more honest name for this would be mBufferAllocationAttempted, since the allocations are fallible. :-)

Comment 5

[Paul Adenot (:padenot)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/e4e2ccb1f247

Comment 6

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/e4e2ccb1f247