Bug 191632 – Align Mac WK2 layer flush throttling with iOS

• Status: RESOLVED
• Resolution: FIXED
• Component: Layout and Rendering

[Antti Koivisto]

Currently Mac WK2 uses WebCore side throttling implementation in RenderLayerCompositor. This code has throttling timer per-frame while the actual decision making and layer flushes itself are per page. These timers generate way more flushes than expected in presence of multiple frames. There are also bugs in how flushing state is updated when frames are created dynamically.

On iOS WK2 throttling is implemented on WebKit side and controlled by a per-page timer. Recent fixes also make this implementation visually fast. We should align the Mac implementation and eventually unify them.

[Antti Koivisto]

Created attachment 354807 [details]
patch

[WebKit Commit Bot]

Comment on attachment 354807 [details]
patch

Clearing flags on attachment: 354807

Committed r238178: <https://trac.webkit.org/changeset/238178>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/46064211>

[Truitt Savell]

The changes in https://trac.webkit.org/changeset/238178/webkit

has caused these two tests to begin timing out on MacOS Release WK2:
fast/forms/access-key-mutated.html 
fast/forms/access-key-case-insensitive.html

Repro Command:
run-webkit-tests --root testbuild-238178 fast/forms/access-key-mutated.html fast/forms/access-key-case-insensitive.html --iterations 5 -f

These tests pass instantly on 238177.

[Antti Koivisto]

Filed https://bugs.webkit.org/show_bug.cgi?id=191642 for those, will skip meanwhile

[Antti Koivisto]

Skipped in https://trac.webkit.org/r238187

[Simon Fraser (smfr)]

Comment on attachment 354807 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=354807&action=review

> Source/WebKit/WebProcess/WebPage/mac/TiledCoreAnimationDrawingArea.mm:221
> +    m_hasPendingFlush = true;
> +
> +    if (m_layerTreeStateIsFrozen) {
> +        m_isLayerFlushThrottlingTemporarilyDisabledForInteraction = false;
>          return;
> +    }
> +
> +    if (m_isLayerFlushThrottlingTemporarilyDisabledForInteraction) {
> +        m_isLayerFlushThrottlingTemporarilyDisabledForInteraction = false;
> +        scheduleLayerFlushRunLoopObserver();
> +        m_layerFlushThrottlingTimer.stop();
> +        return;
> +    }
> +
> +    if (m_layerFlushThrottlingTimer.isActive()) {
> +        ASSERT(m_isThrottlingLayerFlushes);
> +        return;
> +    }
> +
> +    if (m_isThrottlingLayerFlushes) {
> +        startLayerFlushThrottlingTimer();
> +        return;
> +    }

So now this code exists in both TiledCoreAnimationDrawingArea and RemoteLayerTreeDrawingArea. Can we share code?

[Antti Koivisto]

> So now this code exists in both TiledCoreAnimationDrawingArea and
> RemoteLayerTreeDrawingArea. Can we share code?

Like the ChangeLog mentions, sharing is the next step.