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[scudo] Separated committed and decommitted entries. #101409

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merged 2 commits into from
Aug 9, 2024
Merged

[scudo] Separated committed and decommitted entries. #101409

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47b46e0
[scudo] Separated committed and decommitted entries.
JoshuaMBa Jul 31, 2024
5f1a768
Merge branch 'llvm:main' into fix_partition_cache_error
JoshuaMBa Aug 9, 2024
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220 changes: 144 additions & 76 deletions compiler-rt/lib/scudo/standalone/secondary.h
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Original file line number Diff line number Diff line change
Expand Up @@ -184,6 +184,14 @@ template <typename T> class NonZeroLengthArray<T, 0> {
template <typename Config, void (*unmapCallBack)(MemMapT &) = unmap>
class MapAllocatorCache {
public:
typedef enum { COMMITTED = 0, DECOMMITTED = 1, NONE } EntryListT;

// TODO: Refactor the intrusive list to support non-pointer link type
typedef struct {
u16 Head;
u16 Tail;
} ListInfo;

void getStats(ScopedString *Str) {
ScopedLock L(Mutex);
uptr Integral;
Expand All @@ -201,13 +209,18 @@ class MapAllocatorCache {
SuccessfulRetrieves, CallsToRetrieve, Integral, Fractional);
Str->append("Cache Entry Info (Most Recent -> Least Recent):\n");

for (u32 I = LRUHead; I != CachedBlock::InvalidEntry; I = Entries[I].Next) {
CachedBlock &Entry = Entries[I];
Str->append(" StartBlockAddress: 0x%zx, EndBlockAddress: 0x%zx, "
"BlockSize: %zu %s\n",
Entry.CommitBase, Entry.CommitBase + Entry.CommitSize,
Entry.CommitSize, Entry.Time == 0 ? "[R]" : "");
}
auto printList = [&](EntryListT ListType) REQUIRES(Mutex) {
for (u32 I = EntryLists[ListType].Head; I != CachedBlock::InvalidEntry;
I = Entries[I].Next) {
CachedBlock &Entry = Entries[I];
Str->append(" StartBlockAddress: 0x%zx, EndBlockAddress: 0x%zx, "
"BlockSize: %zu %s\n",
Entry.CommitBase, Entry.CommitBase + Entry.CommitSize,
Entry.CommitSize, Entry.Time == 0 ? "[R]" : "");
}
};
printList(COMMITTED);
printList(DECOMMITTED);
}

// Ensure the default maximum specified fits the array.
Expand All @@ -231,8 +244,10 @@ class MapAllocatorCache {
setOption(Option::ReleaseInterval, static_cast<sptr>(ReleaseToOsInterval));

// The cache is initially empty
LRUHead = CachedBlock::InvalidEntry;
LRUTail = CachedBlock::InvalidEntry;
EntryLists[COMMITTED].Head = CachedBlock::InvalidEntry;
EntryLists[COMMITTED].Tail = CachedBlock::InvalidEntry;
EntryLists[DECOMMITTED].Head = CachedBlock::InvalidEntry;
EntryLists[DECOMMITTED].Tail = CachedBlock::InvalidEntry;

// Available entries will be retrieved starting from the beginning of the
// Entries array
Expand All @@ -250,7 +265,6 @@ class MapAllocatorCache {
const s32 Interval = atomic_load_relaxed(&ReleaseToOsIntervalMs);
u64 Time;
CachedBlock Entry;

Entry.CommitBase = CommitBase;
Entry.CommitSize = CommitSize;
Entry.BlockBegin = BlockBegin;
Expand Down Expand Up @@ -312,18 +326,27 @@ class MapAllocatorCache {
Entry = PrevEntry;
}

// All excess entries are evicted from the cache
// All excess entries are evicted from the cache.
// DECOMMITTED entries, being older than the COMMITTED
// entries, are evicted first in least recently used (LRU)
// fashioned followed by the COMMITTED entries
while (needToEvict()) {
EntryListT EvictionListType;
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if (EntryLists[DECOMMITTED].Tail == CachedBlock::InvalidEntry)
EvictionListType = COMMITTED;
else
EvictionListType = DECOMMITTED;
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// Save MemMaps of evicted entries to perform unmap outside of lock
EvictionMemMaps.push_back(Entries[LRUTail].MemMap);
remove(LRUTail);
EvictionMemMaps.push_back(
Entries[EntryLists[EvictionListType].Tail].MemMap);
remove(EntryLists[EvictionListType].Tail, EvictionListType);
}

insert(Entry);
insert(Entry, (Entry.Time == 0) ? DECOMMITTED : COMMITTED);

if (OldestTime == 0)
OldestTime = Entry.Time;
} while (0);
} while (0); // ScopedLock L(Mutex);

for (MemMapT &EvictMemMap : EvictionMemMaps)
unmapCallBack(EvictMemMap);
Expand All @@ -340,17 +363,14 @@ class MapAllocatorCache {
// 10% of the requested size proved to be the optimal choice for
// retrieving cached blocks after testing several options.
constexpr u32 FragmentedBytesDivisor = 10;
bool Found = false;
CachedBlock Entry;
uptr OptimalFitIndex = CachedBlock::InvalidEntry;
uptr MinDiff = UINTPTR_MAX;
EntryListT OptimalFitListType = NONE;
EntryHeaderPos = 0;
{
ScopedLock L(Mutex);
CallsToRetrieve++;
if (EntriesCount == 0)
return {};
u32 OptimalFitIndex = 0;
uptr MinDiff = UINTPTR_MAX;
for (u32 I = LRUHead; I != CachedBlock::InvalidEntry;

auto FindAvailableEntry = [&](EntryListT ListType) REQUIRES(Mutex) {
for (uptr I = EntryLists[ListType].Head; I != CachedBlock::InvalidEntry;
I = Entries[I].Next) {
const uptr CommitBase = Entries[I].CommitBase;
const uptr CommitSize = Entries[I].CommitSize;
Expand All @@ -360,34 +380,48 @@ class MapAllocatorCache {
if (HeaderPos > CommitBase + CommitSize)
continue;
if (HeaderPos < CommitBase ||
AllocPos > CommitBase + PageSize * MaxUnusedCachePages) {
AllocPos > CommitBase + PageSize * MaxUnusedCachePages)
continue;
}
Found = true;

const uptr Diff = HeaderPos - CommitBase;
// immediately use a cached block if it's size is close enough to the
// requested size.
// immediately use a cached block if it's size is close enough to
// the requested size.
const uptr MaxAllowedFragmentedBytes =
(CommitBase + CommitSize - HeaderPos) / FragmentedBytesDivisor;
if (Diff <= MaxAllowedFragmentedBytes) {
OptimalFitIndex = I;
EntryHeaderPos = HeaderPos;
break;
OptimalFitListType = ListType;
return true;
}

// keep track of the smallest cached block
// that is greater than (AllocSize + HeaderSize)
if (Diff > MinDiff)
continue;
OptimalFitIndex = I;
MinDiff = Diff;
OptimalFitListType = ListType;
EntryHeaderPos = HeaderPos;
}
if (Found) {
Entry = Entries[OptimalFitIndex];
remove(OptimalFitIndex);
SuccessfulRetrieves++;
}
}
return (OptimalFitIndex != CachedBlock::InvalidEntry);
};

{
ScopedLock L(Mutex);
CallsToRetrieve++;
if (EntriesCount == 0)
return {};

// Prioritize valid fit from COMMITTED entries over
// optimal fit from DECOMMITTED entries
if (!FindAvailableEntry(COMMITTED) && !FindAvailableEntry(DECOMMITTED))
return {};

Entry = Entries[OptimalFitIndex];
remove(OptimalFitIndex, OptimalFitListType);
SuccessfulRetrieves++;
} // ScopedLock L(Mutex);

return Entry;
}
Expand Down Expand Up @@ -432,10 +466,15 @@ class MapAllocatorCache {
Quarantine[I].invalidate();
}
}
for (u32 I = LRUHead; I != CachedBlock::InvalidEntry; I = Entries[I].Next) {
Entries[I].MemMap.setMemoryPermission(Entries[I].CommitBase,
Entries[I].CommitSize, 0);
}
auto disableLists = [&](EntryListT EntryList) REQUIRES(Mutex) {
for (u32 I = EntryLists[EntryList].Head; I != CachedBlock::InvalidEntry;
I = Entries[I].Next) {
Entries[I].MemMap.setMemoryPermission(Entries[I].CommitBase,
Entries[I].CommitSize, 0);
}
};
disableLists(COMMITTED);
disableLists(DECOMMITTED);
QuarantinePos = -1U;
}

Expand All @@ -450,7 +489,7 @@ class MapAllocatorCache {
return (EntriesCount >= atomic_load_relaxed(&MaxEntriesCount));
}

void insert(const CachedBlock &Entry) REQUIRES(Mutex) {
void insert(const CachedBlock &Entry, EntryListT ListType) REQUIRES(Mutex) {
DCHECK_LT(EntriesCount, atomic_load_relaxed(&MaxEntriesCount));

// Cache should be populated with valid entries when not empty
Expand All @@ -459,66 +498,86 @@ class MapAllocatorCache {
u32 FreeIndex = AvailableHead;
AvailableHead = Entries[AvailableHead].Next;

if (EntriesCount == 0) {
LRUTail = static_cast<u16>(FreeIndex);
} else {
// Check list order
if (EntriesCount > 1)
DCHECK_GE(Entries[LRUHead].Time, Entries[Entries[LRUHead].Next].Time);
Entries[LRUHead].Prev = static_cast<u16>(FreeIndex);
}

Entries[FreeIndex] = Entry;
Entries[FreeIndex].Next = LRUHead;
Entries[FreeIndex].Prev = CachedBlock::InvalidEntry;
LRUHead = static_cast<u16>(FreeIndex);
pushFront(FreeIndex, ListType);
EntriesCount++;

if (Entries[EntryLists[ListType].Head].Next != CachedBlock::InvalidEntry) {
DCHECK_GE(Entries[EntryLists[ListType].Head].Time,
Entries[Entries[EntryLists[ListType].Head].Next].Time);
}
// Availability stack should not have available entries when all entries
// are in use
if (EntriesCount == Config::getEntriesArraySize())
DCHECK_EQ(AvailableHead, CachedBlock::InvalidEntry);
}

void remove(uptr I) REQUIRES(Mutex) {
DCHECK(Entries[I].isValid());

Entries[I].invalidate();

if (I == LRUHead)
LRUHead = Entries[I].Next;
// Joins the entries adjacent to Entries[I], effectively
// unlinking Entries[I] from the list
void unlink(uptr I, EntryListT ListType) REQUIRES(Mutex) {
if (I == EntryLists[ListType].Head)
EntryLists[ListType].Head = Entries[I].Next;
else
Entries[Entries[I].Prev].Next = Entries[I].Next;

if (I == LRUTail)
LRUTail = Entries[I].Prev;
if (I == EntryLists[ListType].Tail)
EntryLists[ListType].Tail = Entries[I].Prev;
else
Entries[Entries[I].Next].Prev = Entries[I].Prev;
}

// Invalidates Entries[I], removes Entries[I] from list, and pushes
// Entries[I] onto the stack of available entries
void remove(uptr I, EntryListT ListType) REQUIRES(Mutex) {
DCHECK(Entries[I].isValid());

Entries[I].invalidate();

unlink(I, ListType);
Entries[I].Next = AvailableHead;
AvailableHead = static_cast<u16>(I);
EntriesCount--;

// Cache should not have valid entries when not empty
if (EntriesCount == 0) {
DCHECK_EQ(LRUHead, CachedBlock::InvalidEntry);
DCHECK_EQ(LRUTail, CachedBlock::InvalidEntry);
DCHECK_EQ(EntryLists[COMMITTED].Head, CachedBlock::InvalidEntry);
DCHECK_EQ(EntryLists[COMMITTED].Tail, CachedBlock::InvalidEntry);
DCHECK_EQ(EntryLists[DECOMMITTED].Head, CachedBlock::InvalidEntry);
DCHECK_EQ(EntryLists[DECOMMITTED].Tail, CachedBlock::InvalidEntry);
}
}

inline void pushFront(uptr I, EntryListT ListType) REQUIRES(Mutex) {
if (EntryLists[ListType].Tail == CachedBlock::InvalidEntry)
EntryLists[ListType].Tail = static_cast<u16>(I);
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else
Entries[EntryLists[ListType].Head].Prev = static_cast<u16>(I);

Entries[I].Next = EntryLists[ListType].Head;
Entries[I].Prev = CachedBlock::InvalidEntry;
EntryLists[ListType].Head = static_cast<u16>(I);
}

void empty() {
MemMapT MapInfo[Config::getEntriesArraySize()];
uptr N = 0;
{
ScopedLock L(Mutex);
for (uptr I = 0; I < Config::getEntriesArraySize(); I++) {
if (!Entries[I].isValid())
continue;
MapInfo[N] = Entries[I].MemMap;
remove(I);
N++;
}
auto emptyList = [&](EntryListT ListType) REQUIRES(Mutex) {
for (uptr I = EntryLists[ListType].Head;
I != CachedBlock::InvalidEntry;) {
uptr ToRemove = I;
I = Entries[I].Next;
MapInfo[N] = Entries[ToRemove].MemMap;
remove(ToRemove, ListType);
N++;
}
};
emptyList(COMMITTED);
emptyList(DECOMMITTED);
EntriesCount = 0;
for (uptr I = 0; I < Config::getEntriesArraySize(); I++)
DCHECK(!Entries[I].isValid());
}
for (uptr I = 0; I < N; I++) {
MemMapT &MemMap = MapInfo[I];
Expand All @@ -545,8 +604,14 @@ class MapAllocatorCache {
OldestTime = 0;
for (uptr I = 0; I < Config::getQuarantineSize(); I++)
releaseIfOlderThan(Quarantine[I], Time);
for (uptr I = 0; I < Config::getEntriesArraySize(); I++)
for (u16 I = EntryLists[COMMITTED].Head; I != CachedBlock::InvalidEntry;
I = Entries[I].Next) {
if (Entries[I].Time && Entries[I].Time <= Time) {
unlink(I, COMMITTED);
pushFront(I, DECOMMITTED);
}
releaseIfOlderThan(Entries[I], Time);
}
}

HybridMutex Mutex;
Expand All @@ -563,10 +628,12 @@ class MapAllocatorCache {
NonZeroLengthArray<CachedBlock, Config::getQuarantineSize()>
Quarantine GUARDED_BY(Mutex) = {};

// The LRUHead of the cache is the most recently used cache entry
u16 LRUHead GUARDED_BY(Mutex) = 0;
// The LRUTail of the cache is the least recently used cache entry
u16 LRUTail GUARDED_BY(Mutex) = 0;
// EntryLists stores the head and tail indices of all
// lists being used to store valid cache entries.
// Currently there are lists storing COMMITTED and DECOMMITTED entries.
// COMMITTED entries have memory chunks that have not been released to the OS
// DECOMMITTED entries have memory chunks that have been released to the OS
ListInfo EntryLists[2] GUARDED_BY(Mutex) = {};
// The AvailableHead is the top of the stack of available entries
u16 AvailableHead GUARDED_BY(Mutex) = 0;
};
Expand Down Expand Up @@ -706,6 +773,7 @@ MapAllocator<Config>::tryAllocateFromCache(const Options &Options, uptr Size,
}
return Ptr;
}

// As with the Primary, the size passed to this function includes any desired
// alignment, so that the frontend can align the user allocation. The hint
// parameter allows us to unmap spurious memory when dealing with larger
Expand Down
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