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gecko-dev/image/SurfaceCache.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/**
* SurfaceCache is a service for caching temporary surfaces in imagelib.
*/
#include "SurfaceCache.h"
#include <algorithm>
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/Likely.h"
#include "mozilla/Move.h"
#include "mozilla/Mutex.h"
#include "mozilla/Pair.h"
#include "mozilla/RefPtr.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/Tuple.h"
#include "nsIMemoryReporter.h"
#include "gfx2DGlue.h"
#include "gfxPattern.h" // Workaround for flaw in bug 921753 part 2.
#include "gfxPlatform.h"
#include "gfxPrefs.h"
#include "imgFrame.h"
#include "Image.h"
#include "LookupResult.h"
#include "nsExpirationTracker.h"
#include "nsHashKeys.h"
#include "nsRefPtrHashtable.h"
#include "nsSize.h"
#include "nsTArray.h"
#include "prsystem.h"
#include "ShutdownTracker.h"
#include "SVGImageContext.h"
using std::max;
using std::min;
namespace mozilla {
using namespace gfx;
namespace image {
class CachedSurface;
class SurfaceCacheImpl;
///////////////////////////////////////////////////////////////////////////////
// Static Data
///////////////////////////////////////////////////////////////////////////////
// The single surface cache instance.
static StaticRefPtr<SurfaceCacheImpl> sInstance;
///////////////////////////////////////////////////////////////////////////////
// SurfaceCache Implementation
///////////////////////////////////////////////////////////////////////////////
/**
* Cost models the cost of storing a surface in the cache. Right now, this is
* simply an estimate of the size of the surface in bytes, but in the future it
* may be worth taking into account the cost of rematerializing the surface as
* well.
*/
typedef size_t Cost;
// Placeholders do not have surfaces, but need to be given a trivial cost for
// our invariants to hold.
static const Cost sPlaceholderCost = 1;
static Cost
ComputeCost(const IntSize& aSize, uint32_t aBytesPerPixel)
{
MOZ_ASSERT(aBytesPerPixel == 1 || aBytesPerPixel == 4);
return aSize.width * aSize.height * aBytesPerPixel;
}
/**
* Since we want to be able to make eviction decisions based on cost, we need to
* be able to look up the CachedSurface which has a certain cost as well as the
* cost associated with a certain CachedSurface. To make this possible, in data
* structures we actually store a CostEntry, which contains a weak pointer to
* its associated surface.
*
* To make usage of the weak pointer safe, SurfaceCacheImpl always calls
* StartTracking after a surface is stored in the cache and StopTracking before
* it is removed.
*/
class CostEntry
{
public:
CostEntry(CachedSurface* aSurface, Cost aCost)
: mSurface(aSurface)
, mCost(aCost)
{
MOZ_ASSERT(aSurface, "Must have a surface");
}
CachedSurface* GetSurface() const { return mSurface; }
Cost GetCost() const { return mCost; }
bool operator==(const CostEntry& aOther) const
{
return mSurface == aOther.mSurface &&
mCost == aOther.mCost;
}
bool operator<(const CostEntry& aOther) const
{
return mCost < aOther.mCost ||
(mCost == aOther.mCost && mSurface < aOther.mSurface);
}
private:
CachedSurface* mSurface;
Cost mCost;
};
/**
* A CachedSurface associates a surface with a key that uniquely identifies that
* surface.
*/
class CachedSurface
{
~CachedSurface() { }
public:
MOZ_DECLARE_REFCOUNTED_TYPENAME(CachedSurface)
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(CachedSurface)
CachedSurface(imgFrame* aSurface,
const Cost aCost,
const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey)
: mSurface(aSurface)
, mCost(aCost)
, mImageKey(aImageKey)
, mSurfaceKey(aSurfaceKey)
{
MOZ_ASSERT(!IsPlaceholder() || mCost == sPlaceholderCost,
"Placeholder should have trivial cost");
MOZ_ASSERT(mImageKey, "Must have a valid image key");
}
DrawableFrameRef DrawableRef() const
{
if (MOZ_UNLIKELY(IsPlaceholder())) {
MOZ_ASSERT_UNREACHABLE("Shouldn't call DrawableRef() on a placeholder");
return DrawableFrameRef();
}
return mSurface->DrawableRef();
}
void SetLocked(bool aLocked)
{
if (IsPlaceholder()) {
return; // Can't lock a placeholder.
}
if (aLocked) {
// This may fail, and that's OK. We make no guarantees about whether
// locking is successful if you call SurfaceCache::LockImage() after
// SurfaceCache::Insert().
mDrawableRef = mSurface->DrawableRef();
} else {
mDrawableRef.reset();
}
}
bool IsPlaceholder() const { return !bool(mSurface); }
bool IsLocked() const { return bool(mDrawableRef); }
ImageKey GetImageKey() const { return mImageKey; }
SurfaceKey GetSurfaceKey() const { return mSurfaceKey; }
CostEntry GetCostEntry() { return image::CostEntry(this, mCost); }
nsExpirationState* GetExpirationState() { return &mExpirationState; }
bool IsDecoded() const
{
return !IsPlaceholder() && mSurface->IsImageComplete();
}
// A helper type used by SurfaceCacheImpl::CollectSizeOfSurfaces.
struct MOZ_STACK_CLASS SurfaceMemoryReport
{
SurfaceMemoryReport(nsTArray<SurfaceMemoryCounter>& aCounters,
MallocSizeOf aMallocSizeOf)
: mCounters(aCounters)
, mMallocSizeOf(aMallocSizeOf)
{ }
void Add(CachedSurface* aCachedSurface)
{
MOZ_ASSERT(aCachedSurface, "Should have a CachedSurface");
SurfaceMemoryCounter counter(aCachedSurface->GetSurfaceKey(),
aCachedSurface->IsLocked());
if (aCachedSurface->mSurface) {
counter.SubframeSize() = Some(aCachedSurface->mSurface->GetSize());
size_t heap = 0, nonHeap = 0;
aCachedSurface->mSurface->AddSizeOfExcludingThis(mMallocSizeOf,
heap, nonHeap);
counter.Values().SetDecodedHeap(heap);
counter.Values().SetDecodedNonHeap(nonHeap);
}
mCounters.AppendElement(counter);
}
private:
nsTArray<SurfaceMemoryCounter>& mCounters;
MallocSizeOf mMallocSizeOf;
};
private:
nsExpirationState mExpirationState;
RefPtr<imgFrame> mSurface;
DrawableFrameRef mDrawableRef;
const Cost mCost;
const ImageKey mImageKey;
const SurfaceKey mSurfaceKey;
};
/**
* An ImageSurfaceCache is a per-image surface cache. For correctness we must be
* able to remove all surfaces associated with an image when the image is
* destroyed or invalidated. Since this will happen frequently, it makes sense
* to make it cheap by storing the surfaces for each image separately.
*
* ImageSurfaceCache also keeps track of whether its associated image is locked
* or unlocked.
*/
class ImageSurfaceCache
{
~ImageSurfaceCache() { }
public:
ImageSurfaceCache() : mLocked(false) { }
MOZ_DECLARE_REFCOUNTED_TYPENAME(ImageSurfaceCache)
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ImageSurfaceCache)
typedef
nsRefPtrHashtable<nsGenericHashKey<SurfaceKey>, CachedSurface> SurfaceTable;
bool IsEmpty() const { return mSurfaces.Count() == 0; }
void Insert(const SurfaceKey& aKey, CachedSurface* aSurface)
{
MOZ_ASSERT(aSurface, "Should have a surface");
MOZ_ASSERT(!mLocked || aSurface->IsPlaceholder() || aSurface->IsLocked(),
"Inserting an unlocked surface for a locked image");
mSurfaces.Put(aKey, aSurface);
}
void Remove(CachedSurface* aSurface)
{
MOZ_ASSERT(aSurface, "Should have a surface");
MOZ_ASSERT(mSurfaces.GetWeak(aSurface->GetSurfaceKey()),
"Should not be removing a surface we don't have");
mSurfaces.Remove(aSurface->GetSurfaceKey());
}
already_AddRefed<CachedSurface> Lookup(const SurfaceKey& aSurfaceKey)
{
RefPtr<CachedSurface> surface;
mSurfaces.Get(aSurfaceKey, getter_AddRefs(surface));
return surface.forget();
}
Pair<already_AddRefed<CachedSurface>, MatchType>
LookupBestMatch(const SurfaceKey& aSurfaceKey)
{
// Try for an exact match first.
RefPtr<CachedSurface> exactMatch;
mSurfaces.Get(aSurfaceKey, getter_AddRefs(exactMatch));
if (exactMatch && exactMatch->IsDecoded()) {
return MakePair(exactMatch.forget(), MatchType::EXACT);
}
// There's no perfect match, so find the best match we can.
MatchContext matchContext(aSurfaceKey);
ForEach(TryToImproveMatch, &matchContext);
MatchType matchType;
if (matchContext.mBestMatch) {
if (!exactMatch) {
// No exact match, but we found a substitute.
matchType = MatchType::SUBSTITUTE_BECAUSE_NOT_FOUND;
} else if (exactMatch != matchContext.mBestMatch) {
// The exact match is still decoding, but we found a substitute.
matchType = MatchType::SUBSTITUTE_BECAUSE_PENDING;
} else {
// The exact match is still decoding, but it's the best we've got.
matchType = MatchType::EXACT;
}
} else {
if (exactMatch) {
// We found an "exact match", but since TryToImproveMatch didn't return
// it, it must have been a placeholder.
MOZ_ASSERT(exactMatch->IsPlaceholder());
matchType = MatchType::PENDING;
} else {
// We couldn't find an exact match *or* a substitute.
matchType = MatchType::NOT_FOUND;
}
}
return MakePair(matchContext.mBestMatch.forget(), matchType);
}
void ForEach(SurfaceTable::EnumReadFunction aFunction, void* aData)
{
mSurfaces.EnumerateRead(aFunction, aData);
}
void SetLocked(bool aLocked) { mLocked = aLocked; }
bool IsLocked() const { return mLocked; }
private:
struct MatchContext
{
explicit MatchContext(const SurfaceKey& aIdealKey)
: mIdealKey(aIdealKey)
{ }
const SurfaceKey& mIdealKey;
RefPtr<CachedSurface> mBestMatch;
};
static PLDHashOperator TryToImproveMatch(const SurfaceKey& aSurfaceKey,
CachedSurface* aSurface,
void* aContext)
{
auto context = static_cast<MatchContext*>(aContext);
const SurfaceKey& idealKey = context->mIdealKey;
// We never match a placeholder.
if (aSurface->IsPlaceholder()) {
return PL_DHASH_NEXT;
}
// Matching the animation time and SVG context is required.
if (aSurfaceKey.AnimationTime() != idealKey.AnimationTime() ||
aSurfaceKey.SVGContext() != idealKey.SVGContext()) {
return PL_DHASH_NEXT;
}
// Matching the flags is required.
if (aSurfaceKey.Flags() != idealKey.Flags()) {
return PL_DHASH_NEXT;
}
// Anything is better than nothing! (Within the constraints we just
// checked, of course.)
if (!context->mBestMatch) {
context->mBestMatch = aSurface;
return PL_DHASH_NEXT;
}
MOZ_ASSERT(context->mBestMatch, "Should have a current best match");
// Always prefer completely decoded surfaces.
bool bestMatchIsDecoded = context->mBestMatch->IsDecoded();
if (bestMatchIsDecoded && !aSurface->IsDecoded()) {
return PL_DHASH_NEXT;
}
if (!bestMatchIsDecoded && aSurface->IsDecoded()) {
context->mBestMatch = aSurface;
return PL_DHASH_NEXT;
}
SurfaceKey bestMatchKey = context->mBestMatch->GetSurfaceKey();
// Compare sizes. We use an area-based heuristic here instead of computing a
// truly optimal answer, since it seems very unlikely to make a difference
// for realistic sizes.
int64_t idealArea = idealKey.Size().width * idealKey.Size().height;
int64_t surfaceArea = aSurfaceKey.Size().width * aSurfaceKey.Size().height;
int64_t bestMatchArea =
bestMatchKey.Size().width * bestMatchKey.Size().height;
// If the best match is smaller than the ideal size, prefer bigger sizes.
if (bestMatchArea < idealArea) {
if (surfaceArea > bestMatchArea) {
context->mBestMatch = aSurface;
}
return PL_DHASH_NEXT;
}
// Other, prefer sizes closer to the ideal size, but still not smaller.
if (idealArea <= surfaceArea && surfaceArea < bestMatchArea) {
context->mBestMatch = aSurface;
return PL_DHASH_NEXT;
}
// This surface isn't an improvement over the current best match.
return PL_DHASH_NEXT;
}
SurfaceTable mSurfaces;
bool mLocked;
};
/**
* SurfaceCacheImpl is responsible for determining which surfaces will be cached
* and managing the surface cache data structures. Rather than interact with
* SurfaceCacheImpl directly, client code interacts with SurfaceCache, which
* maintains high-level invariants and encapsulates the details of the surface
* cache's implementation.
*/
class SurfaceCacheImpl final : public nsIMemoryReporter
{
public:
NS_DECL_ISUPPORTS
SurfaceCacheImpl(uint32_t aSurfaceCacheExpirationTimeMS,
uint32_t aSurfaceCacheDiscardFactor,
uint32_t aSurfaceCacheSize)
: mExpirationTracker(aSurfaceCacheExpirationTimeMS)
, mMemoryPressureObserver(new MemoryPressureObserver)
, mMutex("SurfaceCache")
, mDiscardFactor(aSurfaceCacheDiscardFactor)
, mMaxCost(aSurfaceCacheSize)
, mAvailableCost(aSurfaceCacheSize)
, mLockedCost(0)
, mOverflowCount(0)
{
nsCOMPtr<nsIObserverService> os = services::GetObserverService();
if (os) {
os->AddObserver(mMemoryPressureObserver, "memory-pressure", false);
}
}
private:
virtual ~SurfaceCacheImpl()
{
nsCOMPtr<nsIObserverService> os = services::GetObserverService();
if (os) {
os->RemoveObserver(mMemoryPressureObserver, "memory-pressure");
}
UnregisterWeakMemoryReporter(this);
}
public:
void InitMemoryReporter() { RegisterWeakMemoryReporter(this); }
Mutex& GetMutex() { return mMutex; }
InsertOutcome Insert(imgFrame* aSurface,
const Cost aCost,
const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey)
{
// If this is a duplicate surface, refuse to replace the original.
// XXX(seth): Calling Lookup() and then RemoveSurface() does the lookup
// twice. We'll make this more efficient in bug 1185137.
LookupResult result = Lookup(aImageKey, aSurfaceKey, /* aMarkUsed = */ false);
if (MOZ_UNLIKELY(result)) {
return InsertOutcome::FAILURE_ALREADY_PRESENT;
}
if (result.Type() == MatchType::PENDING) {
RemoveSurface(aImageKey, aSurfaceKey);
}
MOZ_ASSERT(result.Type() == MatchType::NOT_FOUND ||
result.Type() == MatchType::PENDING,
"A LookupResult with no surface should be NOT_FOUND or PENDING");
// If this is bigger than we can hold after discarding everything we can,
// refuse to cache it.
if (MOZ_UNLIKELY(!CanHoldAfterDiscarding(aCost))) {
mOverflowCount++;
return InsertOutcome::FAILURE;
}
// Remove elements in order of cost until we can fit this in the cache. Note
// that locked surfaces aren't in mCosts, so we never remove them here.
while (aCost > mAvailableCost) {
MOZ_ASSERT(!mCosts.IsEmpty(),
"Removed everything and it still won't fit");
Remove(mCosts.LastElement().GetSurface());
}
// Locate the appropriate per-image cache. If there's not an existing cache
// for this image, create it.
RefPtr<ImageSurfaceCache> cache = GetImageCache(aImageKey);
if (!cache) {
cache = new ImageSurfaceCache;
mImageCaches.Put(aImageKey, cache);
}
RefPtr<CachedSurface> surface =
new CachedSurface(aSurface, aCost, aImageKey, aSurfaceKey);
// We require that locking succeed if the image is locked and we're not
// inserting a placeholder; the caller may need to know this to handle
// errors correctly.
if (cache->IsLocked() && !surface->IsPlaceholder()) {
surface->SetLocked(true);
if (!surface->IsLocked()) {
return InsertOutcome::FAILURE;
}
}
// Insert.
MOZ_ASSERT(aCost <= mAvailableCost, "Inserting despite too large a cost");
cache->Insert(aSurfaceKey, surface);
StartTracking(surface);
return InsertOutcome::SUCCESS;
}
void Remove(CachedSurface* aSurface)
{
MOZ_ASSERT(aSurface, "Should have a surface");
ImageKey imageKey = aSurface->GetImageKey();
RefPtr<ImageSurfaceCache> cache = GetImageCache(imageKey);
MOZ_ASSERT(cache, "Shouldn't try to remove a surface with no image cache");
// If the surface was not a placeholder, tell its image that we discarded it.
if (!aSurface->IsPlaceholder()) {
static_cast<Image*>(imageKey)->OnSurfaceDiscarded();
}
StopTracking(aSurface);
cache->Remove(aSurface);
// Remove the per-image cache if it's unneeded now. (Keep it if the image is
// locked, since the per-image cache is where we store that state.)
if (cache->IsEmpty() && !cache->IsLocked()) {
mImageCaches.Remove(imageKey);
}
}
void StartTracking(CachedSurface* aSurface)
{
CostEntry costEntry = aSurface->GetCostEntry();
MOZ_ASSERT(costEntry.GetCost() <= mAvailableCost,
"Cost too large and the caller didn't catch it");
mAvailableCost -= costEntry.GetCost();
if (aSurface->IsLocked()) {
mLockedCost += costEntry.GetCost();
MOZ_ASSERT(mLockedCost <= mMaxCost, "Locked more than we can hold?");
} else {
mCosts.InsertElementSorted(costEntry);
// This may fail during XPCOM shutdown, so we need to ensure the object is
// tracked before calling RemoveObject in StopTracking.
mExpirationTracker.AddObject(aSurface);
}
}
void StopTracking(CachedSurface* aSurface)
{
MOZ_ASSERT(aSurface, "Should have a surface");
CostEntry costEntry = aSurface->GetCostEntry();
if (aSurface->IsLocked()) {
MOZ_ASSERT(mLockedCost >= costEntry.GetCost(), "Costs don't balance");
mLockedCost -= costEntry.GetCost();
// XXX(seth): It'd be nice to use an O(log n) lookup here. This is O(n).
MOZ_ASSERT(!mCosts.Contains(costEntry),
"Shouldn't have a cost entry for a locked surface");
} else {
if (MOZ_LIKELY(aSurface->GetExpirationState()->IsTracked())) {
mExpirationTracker.RemoveObject(aSurface);
} else {
// Our call to AddObject must have failed in StartTracking; most likely
// we're in XPCOM shutdown right now.
NS_ASSERTION(ShutdownTracker::ShutdownHasStarted(),
"Not expiration-tracking an unlocked surface!");
}
DebugOnly<bool> foundInCosts = mCosts.RemoveElementSorted(costEntry);
MOZ_ASSERT(foundInCosts, "Lost track of costs for this surface");
}
mAvailableCost += costEntry.GetCost();
MOZ_ASSERT(mAvailableCost <= mMaxCost,
"More available cost than we started with");
}
LookupResult Lookup(const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey,
bool aMarkUsed = true)
{
RefPtr<ImageSurfaceCache> cache = GetImageCache(aImageKey);
if (!cache) {
// No cached surfaces for this image.
return LookupResult(MatchType::NOT_FOUND);
}
RefPtr<CachedSurface> surface = cache->Lookup(aSurfaceKey);
if (!surface) {
// Lookup in the per-image cache missed.
return LookupResult(MatchType::NOT_FOUND);
}
if (surface->IsPlaceholder()) {
return LookupResult(MatchType::PENDING);
}
DrawableFrameRef ref = surface->DrawableRef();
if (!ref) {
// The surface was released by the operating system. Remove the cache
// entry as well.
Remove(surface);
return LookupResult(MatchType::NOT_FOUND);
}
if (aMarkUsed) {
MarkUsed(surface, cache);
}
MOZ_ASSERT(surface->GetSurfaceKey() == aSurfaceKey,
"Lookup() not returning an exact match?");
return LookupResult(Move(ref), MatchType::EXACT);
}
LookupResult LookupBestMatch(const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey)
{
RefPtr<ImageSurfaceCache> cache = GetImageCache(aImageKey);
if (!cache) {
// No cached surfaces for this image.
return LookupResult(MatchType::NOT_FOUND);
}
// Repeatedly look up the best match, trying again if the resulting surface
// has been freed by the operating system, until we can either lock a
// surface for drawing or there are no matching surfaces left.
// XXX(seth): This is O(N^2), but N is expected to be very small. If we
// encounter a performance problem here we can revisit this.
RefPtr<CachedSurface> surface;
DrawableFrameRef ref;
MatchType matchType = MatchType::NOT_FOUND;
while (true) {
Tie(surface, matchType) = cache->LookupBestMatch(aSurfaceKey);
if (!surface) {
return LookupResult(matchType); // Lookup in the per-image cache missed.
}
ref = surface->DrawableRef();
if (ref) {
break;
}
// The surface was released by the operating system. Remove the cache
// entry as well.
Remove(surface);
}
MOZ_ASSERT_IF(matchType == MatchType::EXACT,
surface->GetSurfaceKey() == aSurfaceKey);
MOZ_ASSERT_IF(matchType == MatchType::SUBSTITUTE_BECAUSE_NOT_FOUND ||
matchType == MatchType::SUBSTITUTE_BECAUSE_PENDING,
surface->GetSurfaceKey().SVGContext() == aSurfaceKey.SVGContext() &&
surface->GetSurfaceKey().AnimationTime() == aSurfaceKey.AnimationTime() &&
surface->GetSurfaceKey().Flags() == aSurfaceKey.Flags());
if (matchType == MatchType::EXACT) {
MarkUsed(surface, cache);
}
return LookupResult(Move(ref), matchType);
}
void RemoveSurface(const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey)
{
RefPtr<ImageSurfaceCache> cache = GetImageCache(aImageKey);
if (!cache) {
return; // No cached surfaces for this image.
}
RefPtr<CachedSurface> surface = cache->Lookup(aSurfaceKey);
if (!surface) {
return; // Lookup in the per-image cache missed.
}
Remove(surface);
}
bool CanHold(const Cost aCost) const
{
return aCost <= mMaxCost;
}
void LockImage(const ImageKey aImageKey)
{
RefPtr<ImageSurfaceCache> cache = GetImageCache(aImageKey);
if (!cache) {
cache = new ImageSurfaceCache;
mImageCaches.Put(aImageKey, cache);
}
cache->SetLocked(true);
// We don't relock this image's existing surfaces right away; instead, the
// image should arrange for Lookup() to touch them if they are still useful.
}
void UnlockImage(const ImageKey aImageKey)
{
RefPtr<ImageSurfaceCache> cache = GetImageCache(aImageKey);
if (!cache || !cache->IsLocked()) {
return; // Already unlocked.
}
cache->SetLocked(false);
// Unlock all the surfaces the per-image cache is holding.
cache->ForEach(DoUnlockSurface, this);
}
void UnlockSurfaces(const ImageKey aImageKey)
{
RefPtr<ImageSurfaceCache> cache = GetImageCache(aImageKey);
if (!cache || !cache->IsLocked()) {
return; // Already unlocked.
}
// (Note that we *don't* unlock the per-image cache here; that's the
// difference between this and UnlockImage.)
// Unlock all the surfaces the per-image cache is holding.
cache->ForEach(DoUnlockSurface, this);
}
void RemoveImage(const ImageKey aImageKey)
{
RefPtr<ImageSurfaceCache> cache = GetImageCache(aImageKey);
if (!cache) {
return; // No cached surfaces for this image, so nothing to do.
}
// Discard all of the cached surfaces for this image.
// XXX(seth): This is O(n^2) since for each item in the cache we are
// removing an element from the costs array. Since n is expected to be
// small, performance should be good, but if usage patterns change we should
// change the data structure used for mCosts.
cache->ForEach(DoStopTracking, this);
// The per-image cache isn't needed anymore, so remove it as well.
// This implicitly unlocks the image if it was locked.
mImageCaches.Remove(aImageKey);
}
void DiscardAll()
{
// Remove in order of cost because mCosts is an array and the other data
// structures are all hash tables. Note that locked surfaces are not
// removed, since they aren't present in mCosts.
while (!mCosts.IsEmpty()) {
Remove(mCosts.LastElement().GetSurface());
}
}
void DiscardForMemoryPressure()
{
// Compute our discardable cost. Since locked surfaces aren't discardable,
// we exclude them.
const Cost discardableCost = (mMaxCost - mAvailableCost) - mLockedCost;
MOZ_ASSERT(discardableCost <= mMaxCost, "Discardable cost doesn't add up");
// Our target is to raise our available cost by (1 / mDiscardFactor) of our
// discardable cost - in other words, we want to end up with about
// (discardableCost / mDiscardFactor) fewer bytes stored in the surface
// cache after we're done.
const Cost targetCost = mAvailableCost + (discardableCost / mDiscardFactor);
if (targetCost > mMaxCost - mLockedCost) {
MOZ_ASSERT_UNREACHABLE("Target cost is more than we can discard");
DiscardAll();
return;
}
// Discard surfaces until we've reduced our cost to our target cost.
while (mAvailableCost < targetCost) {
MOZ_ASSERT(!mCosts.IsEmpty(), "Removed everything and still not done");
Remove(mCosts.LastElement().GetSurface());
}
}
void LockSurface(CachedSurface* aSurface)
{
if (aSurface->IsPlaceholder() || aSurface->IsLocked()) {
return;
}
StopTracking(aSurface);
// Lock the surface. This can fail.
aSurface->SetLocked(true);
StartTracking(aSurface);
}
static PLDHashOperator DoStopTracking(const SurfaceKey&,
CachedSurface* aSurface,
void* aCache)
{
static_cast<SurfaceCacheImpl*>(aCache)->StopTracking(aSurface);
return PL_DHASH_NEXT;
}
static PLDHashOperator DoUnlockSurface(const SurfaceKey&,
CachedSurface* aSurface,
void* aCache)
{
if (aSurface->IsPlaceholder() || !aSurface->IsLocked()) {
return PL_DHASH_NEXT;
}
auto cache = static_cast<SurfaceCacheImpl*>(aCache);
cache->StopTracking(aSurface);
aSurface->SetLocked(false);
cache->StartTracking(aSurface);
return PL_DHASH_NEXT;
}
NS_IMETHOD
CollectReports(nsIHandleReportCallback* aHandleReport,
nsISupports* aData,
bool aAnonymize) override
{
MutexAutoLock lock(mMutex);
// We have explicit memory reporting for the surface cache which is more
// accurate than the cost metrics we report here, but these metrics are
// still useful to report, since they control the cache's behavior.
nsresult rv;
rv = MOZ_COLLECT_REPORT("imagelib-surface-cache-estimated-total",
KIND_OTHER, UNITS_BYTES,
(mMaxCost - mAvailableCost),
"Estimated total memory used by the imagelib "
"surface cache.");
NS_ENSURE_SUCCESS(rv, rv);
rv = MOZ_COLLECT_REPORT("imagelib-surface-cache-estimated-locked",
KIND_OTHER, UNITS_BYTES,
mLockedCost,
"Estimated memory used by locked surfaces in the "
"imagelib surface cache.");
NS_ENSURE_SUCCESS(rv, rv);
rv = MOZ_COLLECT_REPORT("imagelib-surface-cache-overflow-count",
KIND_OTHER, UNITS_COUNT,
mOverflowCount,
"Count of how many times the surface cache has hit "
"its capacity and been unable to insert a new "
"surface.");
NS_ENSURE_SUCCESS(rv, rv);
return NS_OK;
}
void CollectSizeOfSurfaces(const ImageKey aImageKey,
nsTArray<SurfaceMemoryCounter>& aCounters,
MallocSizeOf aMallocSizeOf)
{
RefPtr<ImageSurfaceCache> cache = GetImageCache(aImageKey);
if (!cache) {
return; // No surfaces for this image.
}
// Report all surfaces in the per-image cache.
CachedSurface::SurfaceMemoryReport report(aCounters, aMallocSizeOf);
cache->ForEach(DoCollectSizeOfSurface, &report);
}
static PLDHashOperator DoCollectSizeOfSurface(const SurfaceKey&,
CachedSurface* aSurface,
void* aReport)
{
auto report = static_cast<CachedSurface::SurfaceMemoryReport*>(aReport);
report->Add(aSurface);
return PL_DHASH_NEXT;
}
private:
already_AddRefed<ImageSurfaceCache> GetImageCache(const ImageKey aImageKey)
{
RefPtr<ImageSurfaceCache> imageCache;
mImageCaches.Get(aImageKey, getter_AddRefs(imageCache));
return imageCache.forget();
}
// This is similar to CanHold() except that it takes into account the costs of
// locked surfaces. It's used internally in Insert(), but it's not exposed
// publicly because we permit multithreaded access to the surface cache, which
// means that the result would be meaningless: another thread could insert a
// surface or lock an image at any time.
bool CanHoldAfterDiscarding(const Cost aCost) const
{
return aCost <= mMaxCost - mLockedCost;
}
void MarkUsed(CachedSurface* aSurface, ImageSurfaceCache* aCache)
{
if (aCache->IsLocked()) {
LockSurface(aSurface);
} else {
mExpirationTracker.MarkUsed(aSurface);
}
}
struct SurfaceTracker : public nsExpirationTracker<CachedSurface, 2>
{
explicit SurfaceTracker(uint32_t aSurfaceCacheExpirationTimeMS)
: nsExpirationTracker<CachedSurface, 2>(aSurfaceCacheExpirationTimeMS,
"SurfaceTracker")
{ }
protected:
virtual void NotifyExpired(CachedSurface* aSurface) override
{
if (sInstance) {
MutexAutoLock lock(sInstance->GetMutex());
sInstance->Remove(aSurface);
}
}
};
struct MemoryPressureObserver : public nsIObserver
{
NS_DECL_ISUPPORTS
NS_IMETHOD Observe(nsISupports*,
const char* aTopic,
const char16_t*) override
{
if (sInstance && strcmp(aTopic, "memory-pressure") == 0) {
MutexAutoLock lock(sInstance->GetMutex());
sInstance->DiscardForMemoryPressure();
}
return NS_OK;
}
private:
virtual ~MemoryPressureObserver() { }
};
nsTArray<CostEntry> mCosts;
nsRefPtrHashtable<nsPtrHashKey<Image>,
ImageSurfaceCache> mImageCaches;
SurfaceTracker mExpirationTracker;
RefPtr<MemoryPressureObserver> mMemoryPressureObserver;
Mutex mMutex;
const uint32_t mDiscardFactor;
const Cost mMaxCost;
Cost mAvailableCost;
Cost mLockedCost;
size_t mOverflowCount;
};
NS_IMPL_ISUPPORTS(SurfaceCacheImpl, nsIMemoryReporter)
NS_IMPL_ISUPPORTS(SurfaceCacheImpl::MemoryPressureObserver, nsIObserver)
///////////////////////////////////////////////////////////////////////////////
// Public API
///////////////////////////////////////////////////////////////////////////////
/* static */ void
SurfaceCache::Initialize()
{
// Initialize preferences.
MOZ_ASSERT(NS_IsMainThread());
MOZ_ASSERT(!sInstance, "Shouldn't initialize more than once");
// See gfxPrefs for the default values of these preferences.
// Length of time before an unused surface is removed from the cache, in
// milliseconds.
uint32_t surfaceCacheExpirationTimeMS =
gfxPrefs::ImageMemSurfaceCacheMinExpirationMS();
// What fraction of the memory used by the surface cache we should discard
// when we get a memory pressure notification. This value is interpreted as
// 1/N, so 1 means to discard everything, 2 means to discard about half of the
// memory we're using, and so forth. We clamp it to avoid division by zero.
uint32_t surfaceCacheDiscardFactor =
max(gfxPrefs::ImageMemSurfaceCacheDiscardFactor(), 1u);
// Maximum size of the surface cache, in kilobytes.
uint64_t surfaceCacheMaxSizeKB = gfxPrefs::ImageMemSurfaceCacheMaxSizeKB();
// A knob determining the actual size of the surface cache. Currently the
// cache is (size of main memory) / (surface cache size factor) KB
// or (surface cache max size) KB, whichever is smaller. The formula
// may change in the future, though.
// For example, a value of 4 would yield a 256MB cache on a 1GB machine.
// The smallest machines we are likely to run this code on have 256MB
// of memory, which would yield a 64MB cache on this setting.
// We clamp this value to avoid division by zero.
uint32_t surfaceCacheSizeFactor =
max(gfxPrefs::ImageMemSurfaceCacheSizeFactor(), 1u);
// Compute the size of the surface cache.
uint64_t memorySize = PR_GetPhysicalMemorySize();
if (memorySize == 0) {
MOZ_ASSERT_UNREACHABLE("PR_GetPhysicalMemorySize not implemented here");
memorySize = 256 * 1024 * 1024; // Fall back to 256MB.
}
uint64_t proposedSize = memorySize / surfaceCacheSizeFactor;
uint64_t surfaceCacheSizeBytes = min(proposedSize,
surfaceCacheMaxSizeKB * 1024);
uint32_t finalSurfaceCacheSizeBytes =
min(surfaceCacheSizeBytes, uint64_t(UINT32_MAX));
// Create the surface cache singleton with the requested settings. Note that
// the size is a limit that the cache may not grow beyond, but we do not
// actually allocate any storage for surfaces at this time.
sInstance = new SurfaceCacheImpl(surfaceCacheExpirationTimeMS,
surfaceCacheDiscardFactor,
finalSurfaceCacheSizeBytes);
sInstance->InitMemoryReporter();
}
/* static */ void
SurfaceCache::Shutdown()
{
MOZ_ASSERT(NS_IsMainThread());
MOZ_ASSERT(sInstance, "No singleton - was Shutdown() called twice?");
sInstance = nullptr;
}
/* static */ LookupResult
SurfaceCache::Lookup(const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey)
{
if (!sInstance) {
return LookupResult(MatchType::NOT_FOUND);
}
MutexAutoLock lock(sInstance->GetMutex());
return sInstance->Lookup(aImageKey, aSurfaceKey);
}
/* static */ LookupResult
SurfaceCache::LookupBestMatch(const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey)
{
if (!sInstance) {
return LookupResult(MatchType::NOT_FOUND);
}
MutexAutoLock lock(sInstance->GetMutex());
return sInstance->LookupBestMatch(aImageKey, aSurfaceKey);
}
/* static */ InsertOutcome
SurfaceCache::Insert(imgFrame* aSurface,
const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey)
{
if (!sInstance) {
return InsertOutcome::FAILURE;
}
// Refuse null surfaces.
if (!aSurface) {
MOZ_CRASH("Don't pass null surfaces to SurfaceCache::Insert");
}
MutexAutoLock lock(sInstance->GetMutex());
Cost cost = ComputeCost(aSurface->GetSize(), aSurface->GetBytesPerPixel());
return sInstance->Insert(aSurface, cost, aImageKey, aSurfaceKey);
}
/* static */ InsertOutcome
SurfaceCache::InsertPlaceholder(const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey)
{
if (!sInstance) {
return InsertOutcome::FAILURE;
}
MutexAutoLock lock(sInstance->GetMutex());
return sInstance->Insert(nullptr, sPlaceholderCost, aImageKey, aSurfaceKey);
}
/* static */ bool
SurfaceCache::CanHold(const IntSize& aSize, uint32_t aBytesPerPixel /* = 4 */)
{
if (!sInstance) {
return false;
}
Cost cost = ComputeCost(aSize, aBytesPerPixel);
return sInstance->CanHold(cost);
}
/* static */ bool
SurfaceCache::CanHold(size_t aSize)
{
if (!sInstance) {
return false;
}
return sInstance->CanHold(aSize);
}
/* static */ void
SurfaceCache::LockImage(Image* aImageKey)
{
if (sInstance) {
MutexAutoLock lock(sInstance->GetMutex());
return sInstance->LockImage(aImageKey);
}
}
/* static */ void
SurfaceCache::UnlockImage(Image* aImageKey)
{
if (sInstance) {
MutexAutoLock lock(sInstance->GetMutex());
return sInstance->UnlockImage(aImageKey);
}
}
/* static */ void
SurfaceCache::UnlockSurfaces(const ImageKey aImageKey)
{
if (sInstance) {
MutexAutoLock lock(sInstance->GetMutex());
return sInstance->UnlockSurfaces(aImageKey);
}
}
/* static */ void
SurfaceCache::RemoveSurface(const ImageKey aImageKey,
const SurfaceKey& aSurfaceKey)
{
if (sInstance) {
MutexAutoLock lock(sInstance->GetMutex());
sInstance->RemoveSurface(aImageKey, aSurfaceKey);
}
}
/* static */ void
SurfaceCache::RemoveImage(Image* aImageKey)
{
if (sInstance) {
MutexAutoLock lock(sInstance->GetMutex());
sInstance->RemoveImage(aImageKey);
}
}
/* static */ void
SurfaceCache::DiscardAll()
{
if (sInstance) {
MutexAutoLock lock(sInstance->GetMutex());
sInstance->DiscardAll();
}
}
/* static */ void
SurfaceCache::CollectSizeOfSurfaces(const ImageKey aImageKey,
nsTArray<SurfaceMemoryCounter>& aCounters,
MallocSizeOf aMallocSizeOf)
{
if (!sInstance) {
return;
}
MutexAutoLock lock(sInstance->GetMutex());
return sInstance->CollectSizeOfSurfaces(aImageKey, aCounters, aMallocSizeOf);
}
} // namespace image
} // namespace mozilla
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