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rhi: Add a way to get an insight to res.update batch data

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Instead of speculating about resource update batch pools, have a
toggleable debug message that shows exactly what one needs to know. Set
qt.rhi.rub to true to enable. Note that it is not a qCDebug since we do
not want isEnabled() checks no matter how cheap on hot code paths.
Rather, the state of the category is checked just once on
QRhi::create(). As we want some output from QRhiBufferData too, this is
static (setting the bool flag may not be entirely thread safe
technically but we can live with it).

In addition, harden size() and constData() in QRhiBufferData, although
these d != null checks are a waste of time with the current
implementation, but be safe.

Remove the unused QT_RHI_MINIMIZE_POOLS environment variable. This is
forgotten completely by now and serves no practical purpose. Those who
want a proper release of all pools should call releaseCachedResources()
(i.e. QQuickWindow::releaseResources()).

Expand the comments as well.

Change-Id: I4942cf7c3f2ecff47991e42e14c61b432f232170
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
(cherry picked from commit cbab56fdcbff6965d2aafd0c00eebacb7809ceba)
This commit is contained in:
Laszlo Agocs 2024-08-06 18:00:43 +02:00
parent d05438454f
commit e4bd5c631a
2 changed files with 59 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
src/gui/rhi/qrhi.cpp
View File

@ -25,6 +25,7 @@
QT_BEGIN_NAMESPACE
Q_LOGGING_CATEGORY(QRHI_LOG_INFO, "qt.rhi.general")
Q_LOGGING_CATEGORY(QRHI_LOG_RUB, "qt.rhi.rub")
/*!
\class QRhi
@ -8455,6 +8456,8 @@ QRhi::~QRhi()
delete d;
}
bool QRhiImplementation::rubLogEnabled = false;
void QRhiImplementation::prepareForCreate(QRhi *rhi, QRhi::Implementation impl, QRhi::Flags flags)
{
q = rhi;
@ -8467,6 +8470,8 @@ void QRhiImplementation::prepareForCreate(QRhi *rhi, QRhi::Implementation impl,
debugMarkers = flags.testFlag(QRhi::EnableDebugMarkers);
rubLogEnabled = QRHI_LOG_RUB().isDebugEnabled();
implType = impl;
implThread = QThread::currentThread();
}
@ -9265,20 +9270,25 @@ void QRhiResourceUpdateBatch::generateMips(QRhiTexture *tex)
*/
QRhiResourceUpdateBatch *QRhi::nextResourceUpdateBatch()
{
// By default we prefer spreading out the utilization of the 64 batches as
// much as possible, meaning we won't pick the first one even if it's free,
// but prefer picking one after the last picked one. Relevant due to how
// QVLA and QRhiBufferData allocations behind the bufferOps are reused; in
// typical Qt Quick scenes this leads to a form of (eventually) seeding all
// the 64 resource batches with buffer operation data allocations which are
// then reused in subsequent frames. This comes at the expense of using
// more memory, but has proven good results when (CPU) profiling typical
// Quick/Quick3D apps.
// By default we prefer spreading out the utilization of the worst case 64
// (but typically 4) batches as much as possible, meaning we won't pick the
// first one even if it's free, but prefer picking one after the last picked
// one. Relevant due to implicit sharing (the backend may hold on to the
// QRhiBufferData until frame no. current+FramesInFlight-1, but
// implementations may vary), combined with the desire to reuse container
// and QRhiBufferData allocations in bufferOps instead of flooding every
// frame with allocs. See free(). In typical Qt Quick scenes this leads to
// eventually seeding all 4 (or more) resource batches with buffer operation
// data allocations which may (*) then be reused in subsequent frames. This
// comes at the expense of using more memory, but has proven good results
// when (CPU) profiling typical Quick/Quick3D apps.
//
// Prefering memory over performance means that we always pick the first
// free batch, and triggering the aggressive deallocating of all backing
// memory (see trimOpLists) before returning it.
static const bool preferMemoryOverPerformance = qEnvironmentVariableIntValue("QT_RHI_MINIMIZE_POOLS");
// (*) Due to implicit sharing(ish), the exact behavior is unpredictable. If
// a backend holds on to the QRhiBufferData for, e.g., a dynamic buffer
// update, and then there is a new assign() for that same QRhiBufferData
// while the refcount is still 2, it will "detach" (without contents) and
// there is no reuse of the alloc. This is mitigated by the 'choose the one
// afer the last picked one' logic when handing out batches.
auto nextFreeBatch = [this]() -> QRhiResourceUpdateBatch * {
auto isFree = [this](int i) -> QRhiResourceUpdateBatch * {
@ -9287,8 +9297,7 @@ QRhiResourceUpdateBatch *QRhi::nextResourceUpdateBatch()
d->resUpdPoolMap |= mask;
QRhiResourceUpdateBatch *u = d->resUpdPool[i];
QRhiResourceUpdateBatchPrivate::get(u)->poolIndex = i;
if (!preferMemoryOverPerformance)
d->lastResUpdIdx = i;
d->lastResUpdIdx = i;
return u;
}
return nullptr;
@ -9308,6 +9317,7 @@ QRhiResourceUpdateBatch *QRhi::nextResourceUpdateBatch()
QRhiResourceUpdateBatch *u = nextFreeBatch();
if (!u) {
const int oldSize = d->resUpdPool.size();
// 4, 8, 12, ..., up to 64
const int newSize = oldSize + qMin(4, qMax(0, 64 - oldSize));
d->resUpdPool.resize(newSize);
for (int i = oldSize; i < newSize; ++i)
@ -9317,9 +9327,6 @@ QRhiResourceUpdateBatch *QRhi::nextResourceUpdateBatch()
qWarning("Resource update batch pool exhausted (max is 64)");
}
if (preferMemoryOverPerformance && u)
u->d->trimOpLists();
return u;
}
@ -9327,6 +9334,22 @@ void QRhiResourceUpdateBatchPrivate::free()
{
Q_ASSERT(poolIndex >= 0 && rhi->resUpdPool[poolIndex] == q);
if (rhi->rubLogEnabled) {
quint32 bufferDataTotal = 0;
quint32 bufferLargeAllocTotal = 0;
for (const BufferOp &op : std::as_const(bufferOps)) {
bufferDataTotal += op.data.size();
bufferLargeAllocTotal += op.data.largeAlloc(); // alloc when > 1 KB
}
qDebug() << "[rub] release to pool upd.batch #" << poolIndex
<< "/ bufferOps active" << activeBufferOpCount
<< "of" << bufferOps.count()
<< "data" << bufferDataTotal
<< "largeAlloc" << bufferLargeAllocTotal
<< "textureOps active" << activeTextureOpCount
<< "of" << textureOps.count();
}
activeBufferOpCount = 0;
activeTextureOpCount = 0;
@ -10761,6 +10784,9 @@ QRhi::FrameOpResult QRhi::beginFrame(QRhiSwapChain *swapChain, BeginFrameFlags f
if (d->inFrame)
qWarning("Attempted to call beginFrame() within a still active frame; ignored");
if (d->rubLogEnabled)
qDebug("[rub] new frame");
QRhi::FrameOpResult r = !d->inFrame ? d->beginFrame(swapChain, flags) : FrameOpSuccess;
if (r == FrameOpSuccess)
d->inFrame = true;
@ -10909,6 +10935,9 @@ QRhi::FrameOpResult QRhi::beginOffscreenFrame(QRhiCommandBuffer **cb, BeginFrame
if (d->inFrame)
qWarning("Attempted to call beginOffscreenFrame() within a still active frame; ignored");
if (d->rubLogEnabled)
qDebug("[rub] new offscreen frame");
QRhi::FrameOpResult r = !d->inFrame ? d->beginOffscreenFrame(cb, flags) : FrameOpSuccess;
if (r == FrameOpSuccess)
d->inFrame = true;

14
src/gui/rhi/qrhi_p.h
View File

@ -254,9 +254,11 @@ private:
QHash<const void *, QRhi::CleanupCallback> keyedCleanupCallbacks;
QElapsedTimer pipelineCreationTimer;
qint64 accumulatedPipelineCreationTime = 0;
static bool rubLogEnabled;
friend class QRhi;
friend class QRhiResourceUpdateBatchPrivate;
friend class QRhiBufferData;
};
enum QRhiTargetRectBoundMode
@ -352,17 +354,23 @@ public:
}
const char *constData() const
{
return d->size <= QRhiBufferDataPrivate::SMALL_DATA_SIZE ? d->data : d->largeData;
return d ? (d->size <= QRhiBufferDataPrivate::SMALL_DATA_SIZE ? d->data : d->largeData) : nullptr;
}
quint32 size() const
{
return d->size;
return d ? d->size : 0;
}
quint32 largeAlloc() const
{
return d ? d->largeAlloc : 0;
}
void assign(const char *s, quint32 size)
{
if (!d) {
d = new QRhiBufferDataPrivate;
} else if (d->ref != 1) {
if (QRhiImplementation::rubLogEnabled)
qDebug("[rub] QRhiBufferData %p/%p new backing due to no-copy detach, ref was %d", this, d, d->ref);
d->ref -= 1;
d = new QRhiBufferDataPrivate;
}
@ -371,6 +379,8 @@ public:
memcpy(d->data, s, size);
} else {
if (d->largeAlloc < size) {
if (QRhiImplementation::rubLogEnabled)
qDebug("[rub] QRhiBufferData %p/%p new large data allocation %u -> %u", this, d, d->largeAlloc, size);
delete[] d->largeData;
d->largeAlloc = size;
d->largeData = new char[size];