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Commit 29abff83 authored by Robert Carr's avatar Robert Carr
Browse files

Optimize layer traversal 

I found when investigating traces with reported jank from P there
was a large amount of time in handleMessageInvalidate but before
latchBuffer. The only culprit here could be layer traversal itself.
The current algorithm is quite costy requiring producing copies
of sp, allocating a new vector, etc (see makeTraversalList). This CL
optimizes the case where there are no relatives of the current layer.
I found that this does in fact eliminate the new time in
handleMessageInvalidate and also reduces onPreComposition.

Bug:69852584
Test: Manual, comparison of systrace, relative Z still works.
Change-Id: I2d942c1987087aae85decc0480d3622204ed665d
parent 13dd603c

services/surfaceflinger/Layer.cpp

+42 −3
Original line number Diff line number Diff line
@@ -1616,14 +1616,25 @@ int32_t Layer::getZ() const { 
    return mDrawingState.z;

}



bool Layer::usingRelativeZ(LayerVector::StateSet stateSet) {

    const bool useDrawing = stateSet == LayerVector::StateSet::Drawing;

    const State& state = useDrawing ? mDrawingState : mCurrentState;

    return state.zOrderRelativeOf != nullptr;

}



__attribute__((no_sanitize("unsigned-integer-overflow"))) LayerVector Layer::makeTraversalList(

        LayerVector::StateSet stateSet) {

        LayerVector::StateSet stateSet, bool* outSkipRelativeZUsers) {

    LOG_ALWAYS_FATAL_IF(stateSet == LayerVector::StateSet::Invalid,

                        "makeTraversalList received invalid stateSet");

    const bool useDrawing = stateSet == LayerVector::StateSet::Drawing;

    const LayerVector& children = useDrawing ? mDrawingChildren : mCurrentChildren;

    const State& state = useDrawing ? mDrawingState : mCurrentState;



    if (state.zOrderRelatives.size() == 0) {

        *outSkipRelativeZUsers = true;

        return children;

    }



    LayerVector traverse;

    for (const wp<Layer>& weakRelative : state.zOrderRelatives) {

        sp<Layer> strongRelative = weakRelative.promote();
@@ -1647,19 +1658,35 @@ __attribute__((no_sanitize("unsigned-integer-overflow"))) LayerVector Layer::mak 
 * Negatively signed relatives are before 'this' in Z-order.

 */

void Layer::traverseInZOrder(LayerVector::StateSet stateSet, const LayerVector::Visitor& visitor) {

    LayerVector list = makeTraversalList(stateSet);

    // In the case we have other layers who are using a relative Z to us, makeTraversalList will

    // produce a new list for traversing, including our relatives, and not including our children

    // who are relatives of another surface. In the case that there are no relative Z,

    // makeTraversalList returns our children directly to avoid significant overhead.

    // However in this case we need to take the responsibility for filtering children which

    // are relatives of another surface here.

    bool skipRelativeZUsers = false;

    const LayerVector list = makeTraversalList(stateSet, &skipRelativeZUsers);



    size_t i = 0;

    for (; i < list.size(); i++) {

        const auto& relative = list[i];

        if (skipRelativeZUsers && relative->usingRelativeZ(stateSet)) {

            continue;

        }



        if (relative->getZ() >= 0) {

            break;

        }

        relative->traverseInZOrder(stateSet, visitor);

    }



    visitor(this);

    for (; i < list.size(); i++) {

        const auto& relative = list[i];



        if (skipRelativeZUsers && relative->usingRelativeZ(stateSet)) {

            continue;

        }

        relative->traverseInZOrder(stateSet, visitor);

    }

}
@@ -1669,11 +1696,18 @@ void Layer::traverseInZOrder(LayerVector::StateSet stateSet, const LayerVector:: 
 */

void Layer::traverseInReverseZOrder(LayerVector::StateSet stateSet,

                                    const LayerVector::Visitor& visitor) {

    LayerVector list = makeTraversalList(stateSet);

    // See traverseInZOrder for documentation.

    bool skipRelativeZUsers = false;

    LayerVector list = makeTraversalList(stateSet, &skipRelativeZUsers);



    int32_t i = 0;

    for (i = int32_t(list.size()) - 1; i >= 0; i--) {

        const auto& relative = list[i];



        if (skipRelativeZUsers && relative->usingRelativeZ(stateSet)) {

            continue;

        }



        if (relative->getZ() < 0) {

            break;

        }
@@ -1682,6 +1716,11 @@ void Layer::traverseInReverseZOrder(LayerVector::StateSet stateSet, 
    visitor(this);

    for (; i >= 0; i--) {

        const auto& relative = list[i];



        if (skipRelativeZUsers && relative->usingRelativeZ(stateSet)) {

            continue;

        }



        relative->traverseInReverseZOrder(stateSet, visitor);

    }

}

services/surfaceflinger/Layer.h

+2 −1
Original line number Diff line number Diff line
@@ -571,7 +571,7 @@ protected: 


    void setParent(const sp<Layer>& layer);



    LayerVector makeTraversalList(LayerVector::StateSet stateSet);

    LayerVector makeTraversalList(LayerVector::StateSet stateSet, bool* outSkipRelativeZUsers);

    void addZOrderRelative(const wp<Layer>& relative);

    void removeZOrderRelative(const wp<Layer>& relative);
@@ -645,6 +645,7 @@ public: 


protected:

    // -----------------------------------------------------------------------

    bool usingRelativeZ(LayerVector::StateSet stateSet);



    bool mPremultipliedAlpha;

    String8 mName;