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Less contention in cache (Part 3)

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This commit is contained in:
kssenii 2024-03-11 16:09:14 +01:00
parent d4146c1e26
commit 96778ff6ae
10 changed files with 102 additions and 45 deletions
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3
src/Common/ProfileEvents.cpp
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@ -459,7 +459,8 @@ The server successfully detected this situation and will download merged part fr
M(FilesystemCacheLoadMetadataMicroseconds, "Time spent loading filesystem cache metadata") \
M(FilesystemCacheEvictedBytes, "Number of bytes evicted from filesystem cache") \
M(FilesystemCacheEvictedFileSegments, "Number of file segments evicted from filesystem cache") \
M(FilesystemCacheEvictionSkippedFileSegments, "Number of file segments skipped for eviction because of being unreleasable") \
M(FilesystemCacheEvictionSkippedFileSegments, "Number of file segments skipped for eviction because of being in unreleasable state") \
M(FilesystemCacheEvictionSkippedEvictingFileSegments, "Number of file segments skipped for eviction because of being in evicting state") \
M(FilesystemCacheEvictionTries, "Number of filesystem cache eviction attempts") \
M(FilesystemCacheLockKeyMicroseconds, "Lock cache key time") \
M(FilesystemCacheLockMetadataMicroseconds, "Lock filesystem cache metadata time") \

23
src/Interpreters/Cache/EvictionCandidates.cpp
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@ -32,7 +32,7 @@ void EvictionCandidates::add(LockedKey & locked_key, const FileSegmentMetadataPt
++candidates_size;
}
void EvictionCandidates::evict(FileCacheQueryLimit::QueryContext * query_context, const CacheGuard::Lock & lock)
void EvictionCandidates::evict()
{
if (candidates.empty())
return;
@ -59,14 +59,27 @@ void EvictionCandidates::evict(FileCacheQueryLimit::QueryContext * query_context
ProfileEvents::increment(ProfileEvents::FilesystemCacheEvictedBytes, segment->range().size());
locked_key->removeFileSegment(segment->offset(), segment->lock());
queue_it->remove(lock);
if (query_context)
query_context->remove(segment->key(), segment->offset(), lock);
queue_it->invalidate();
to_evict.pop_back();
}
}
}
void EvictionCandidates::finalize(FileCacheQueryLimit::QueryContext * query_context, const CacheGuard::Lock & lock)
{
for (const auto & it : invalidated_queue_entries)
{
if (query_context)
{
const auto & entry = it->getEntry();
query_context->remove(entry->key, entry->offset, lock);
}
it->remove(lock);
}
if (finalize_eviction_func)
finalize_eviction_func(lock);
}
}

9
src/Interpreters/Cache/EvictionCandidates.h
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@ -11,7 +11,9 @@ public:
void add(LockedKey & locked_key, const FileSegmentMetadataPtr & candidate);
void evict(FileCacheQueryLimit::QueryContext * query_context, const CacheGuard::Lock &);
void evict();
void finalize(FileCacheQueryLimit::QueryContext * query_context, const CacheGuard::Lock & lock);
size_t size() const { return candidates_size; }
@ -19,6 +21,9 @@ public:
auto end() const { return candidates.end(); }
using FinalizeEvictionFunc = std::function<void(const CacheGuard::Lock & lk)>;
void setFinalizeEvictionFunc(FinalizeEvictionFunc && func) { finalize_eviction_func = func; }
private:
struct KeyCandidates
{
@ -28,6 +33,8 @@ private:
std::unordered_map<FileCacheKey, KeyCandidates> candidates;
size_t candidates_size = 0;
std::vector<IFileCachePriority::IteratorPtr> invalidated_queue_entries;
FinalizeEvictionFunc finalize_eviction_func;
};
using EvictionCandidatesPtr = std::unique_ptr<EvictionCandidates>;

34
src/Interpreters/Cache/FileCache.cpp
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@ -814,12 +814,10 @@ bool FileCache::tryReserve(
}
EvictionCandidates eviction_candidates;
IFileCachePriority::FinalizeEvictionFunc finalize_eviction_func;
if (query_priority)
{
if (!query_priority->collectCandidatesForEviction(
size, reserve_stat, eviction_candidates, {}, finalize_eviction_func, user.user_id, cache_lock))
if (!query_priority->collectCandidatesForEviction(size, reserve_stat, eviction_candidates, {}, user.user_id, cache_lock))
return false;
LOG_TEST(log, "Query limits satisfied (while reserving for {}:{})", file_segment.key(), file_segment.offset());
@ -832,26 +830,38 @@ bool FileCache::tryReserve(
auto queue_iterator = file_segment.getQueueIterator();
chassert(!queue_iterator || file_segment.getReservedSize() > 0);
if (!main_priority->collectCandidatesForEviction(
size, reserve_stat, eviction_candidates, queue_iterator, finalize_eviction_func, user.user_id, cache_lock))
if (!main_priority->collectCandidatesForEviction(size, reserve_stat, eviction_candidates, queue_iterator, user.user_id, cache_lock))
return false;
/// Let's release cache lock if we are going to remove files from filesystem.
bool release_lock = eviction_candidates.size() > 0;
if (release_lock)
cache_lock.unlock();
if (!file_segment.getKeyMetadata()->createBaseDirectory())
return false;
eviction_candidates.evict(query_context.get(), cache_lock);
/// Remove eviction candidates from filesystem.
eviction_candidates.evict();
if (finalize_eviction_func)
finalize_eviction_func(cache_lock);
/// Take cache lock again.
if (release_lock)
cache_lock.lock();
/// Remove invalidated queue entries and execute (only for SLRU) finalize func.
eviction_candidates.finalize(query_context.get(), cache_lock);
/// Space reservation is incremental, so file_segment_metadata is created first (with state Empty),
/// and queue_iterator is assigned on first space reservation attempt
/// (so it is nullptr here if we are reserving for the first time).
if (queue_iterator)
{
queue_iterator->updateSize(size);
/// Increase size of queue entry.
queue_iterator->incrementSize(size, cache_lock);
}
else
{
/// Space reservation is incremental, so file_segment_metadata is created first (with state empty),
/// and getQueueIterator() is assigned on first space reservation attempt.
/// Create a new queue entry and assign currently reserved size to it.
queue_iterator = main_priority->add(file_segment.getKeyMetadata(), file_segment.offset(), size, user, cache_lock);
file_segment.setQueueIterator(queue_iterator);
}
@ -863,7 +873,7 @@ bool FileCache::tryReserve(
{
auto query_queue_it = query_context->tryGet(file_segment.key(), file_segment.offset(), cache_lock);
if (query_queue_it)
query_queue_it->updateSize(size);
query_queue_it->incrementSize(size, cache_lock);
else
query_context->add(file_segment.getKeyMetadata(), file_segment.offset(), size, user, cache_lock);
}

9
src/Interpreters/Cache/IFileCachePriority.h
View File

@ -45,7 +45,12 @@ public:
virtual size_t increasePriority(const CacheGuard::Lock &) = 0;
virtual void updateSize(int64_t size) = 0;
/// Note: IncrementSize unlike decrementSize requires a cache lock, because
/// it requires more consistency guarantees for eviction.
virtual void incrementSize(size_t size, const CacheGuard::Lock &) = 0;
virtual void decrementSize(size_t size) = 0;
virtual void remove(const CacheGuard::Lock &) = 0;
@ -93,13 +98,11 @@ public:
virtual PriorityDumpPtr dump(const CacheGuard::Lock &) = 0;
using FinalizeEvictionFunc = std::function<void(const CacheGuard::Lock & lk)>;
virtual bool collectCandidatesForEviction(
size_t size,
FileCacheReserveStat & stat,
EvictionCandidates & res,
IFileCachePriority::IteratorPtr reservee,
FinalizeEvictionFunc & finalize_eviction_func,
const UserID & user_id,
const CacheGuard::Lock &) = 0;

26
src/Interpreters/Cache/LRUFileCachePriority.cpp
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@ -15,6 +15,7 @@ namespace CurrentMetrics
namespace ProfileEvents
{
extern const Event FilesystemCacheEvictionSkippedFileSegments;
extern const Event FilesystemCacheEvictionSkippedEvictingFileSegments;
extern const Event FilesystemCacheEvictionTries;
extern const Event FilesystemCacheEvictMicroseconds;
extern const Event FilesystemCacheEvictedBytes;
@ -223,7 +224,6 @@ bool LRUFileCachePriority::collectCandidatesForEviction(
FileCacheReserveStat & stat,
EvictionCandidates & res,
IFileCachePriority::IteratorPtr,
FinalizeEvictionFunc &,
const UserID &,
const CacheGuard::Lock & lock)
{
@ -237,7 +237,11 @@ bool LRUFileCachePriority::collectCandidatesForEviction(
const auto & file_segment = segment_metadata->file_segment;
chassert(file_segment->assertCorrectness());
if (segment_metadata->releasable())
if (segment_metadata->evicting())
{
ProfileEvents::increment(ProfileEvents::FilesystemCacheEvictionSkippedEvictingFileSegments);
}
else if (segment_metadata->releasable())
{
res.add(locked_key, segment_metadata);
stat.update(segment_metadata->size(), file_segment->getKind(), true);
@ -375,20 +379,34 @@ void LRUFileCachePriority::LRUIterator::invalidate()
entry->size = 0;
}
void LRUFileCachePriority::LRUIterator::updateSize(int64_t size)
void LRUFileCachePriority::LRUIterator::incrementSize(size_t size, const CacheGuard::Lock &)
{
assertValid();
const auto & entry = *iterator;
LOG_TEST(
cache_priority->log,
"Update size with {} in LRU queue for key: {}, offset: {}, previous size: {}",
"Increment size with {} in LRU queue for key: {}, offset: {}, previous size: {}",
size, entry->key, entry->offset, entry->size);
cache_priority->updateSize(size);
entry->size += size;
}
void LRUFileCachePriority::LRUIterator::decrementSize(size_t size)
{
assertValid();
const auto & entry = *iterator;
LOG_TEST(
cache_priority->log,
"Decrement size with {} in LRU queue for key: {}, offset: {}, previous size: {}",
size, entry->key, entry->offset, entry->size);
cache_priority->updateSize(-size);
entry->size -= size;
}
size_t LRUFileCachePriority::LRUIterator::increasePriority(const CacheGuard::Lock &)
{
assertValid();

5
src/Interpreters/Cache/LRUFileCachePriority.h
View File

@ -47,7 +47,6 @@ public:
FileCacheReserveStat & stat,
EvictionCandidates & res,
IFileCachePriority::IteratorPtr reservee,
FinalizeEvictionFunc & finalize_eviction_func,
const UserID & user_id,
const CacheGuard::Lock &) override;
@ -114,7 +113,9 @@ public:
void invalidate() override;
void updateSize(int64_t size) override;
void incrementSize(size_t size, const CacheGuard::Lock &) override;
void decrementSize(size_t size) override;
QueueEntryType getType() const override { return QueueEntryType::LRU; }

2
src/Interpreters/Cache/Metadata.cpp
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@ -1012,7 +1012,7 @@ void LockedKey::shrinkFileSegmentToDownloadedSize(
file_segment->cache, key_metadata, file_segment->queue_iterator);
if (diff)
metadata->getQueueIterator()->updateSize(-diff);
metadata->getQueueIterator()->decrementSize(diff);
chassert(file_segment->assertCorrectnessUnlocked(segment_lock));
}

31
src/Interpreters/Cache/SLRUFileCachePriority.cpp
View File

@ -101,7 +101,6 @@ bool SLRUFileCachePriority::collectCandidatesForEviction(
FileCacheReserveStat & stat,
EvictionCandidates & res,
IFileCachePriority::IteratorPtr reservee,
FinalizeEvictionFunc & finalize_eviction_func,
const UserID & user_id,
const CacheGuard::Lock & lock)
{
@ -109,7 +108,7 @@ bool SLRUFileCachePriority::collectCandidatesForEviction(
/// for a corresponding file segment, so it will be directly put into probationary queue.
if (!reservee)
{
return probationary_queue.collectCandidatesForEviction(size, stat, res, reservee, finalize_eviction_func, user_id, lock);
return probationary_queue.collectCandidatesForEviction(size, stat, res, reservee, user_id, lock);
}
/// If `it` not nullptr (e.g. is already in some queue),
@ -117,7 +116,7 @@ bool SLRUFileCachePriority::collectCandidatesForEviction(
/// (in order to know where we need to free space).
if (!assert_cast<SLRUIterator *>(reservee.get())->is_protected)
{
return probationary_queue.collectCandidatesForEviction(size, stat, res, reservee, finalize_eviction_func, user_id, lock);
return probationary_queue.collectCandidatesForEviction(size, stat, res, reservee, user_id, lock);
}
/// Entry is in protected queue.
@ -132,18 +131,17 @@ bool SLRUFileCachePriority::collectCandidatesForEviction(
/// required to make space for additionary `size` bytes for entry.
auto downgrade_candidates = std::make_shared<EvictionCandidates>();
FileCacheReserveStat downgrade_stat;
FinalizeEvictionFunc noop;
if (!protected_queue.collectCandidatesForEviction(size, downgrade_stat, *downgrade_candidates, reservee, noop, user_id, lock))
if (!protected_queue.collectCandidatesForEviction(size, downgrade_stat, *downgrade_candidates, reservee, user_id, lock))
return false;
const size_t size_to_downgrade = downgrade_stat.stat.releasable_size;
if (!probationary_queue.canFit(size_to_downgrade, lock)
&& !probationary_queue.collectCandidatesForEviction(size_to_downgrade, stat, res, reservee, noop, user_id, lock))
&& !probationary_queue.collectCandidatesForEviction(size_to_downgrade, stat, res, reservee, user_id, lock))
return false;
finalize_eviction_func = [=, this](const CacheGuard::Lock & lk) mutable
res.setFinalizeEvictionFunc([=, this](const CacheGuard::Lock & lk) mutable
{
for (const auto & [key, key_candidates] : *downgrade_candidates)
{
@ -154,7 +152,7 @@ bool SLRUFileCachePriority::collectCandidatesForEviction(
candidate_it->is_protected = false;
}
}
};
});
return true;
}
@ -186,9 +184,8 @@ void SLRUFileCachePriority::increasePriority(SLRUIterator & iterator, const Cach
/// queue to probationary queue.
EvictionCandidates downgrade_candidates;
FileCacheReserveStat downgrade_stat;
FinalizeEvictionFunc noop;
if (!protected_queue.collectCandidatesForEviction(size, downgrade_stat, downgrade_candidates, {}, noop, "", lock))
if (!protected_queue.collectCandidatesForEviction(size, downgrade_stat, downgrade_candidates, {}, "", lock))
{
/// We cannot make space for entry to be moved to protected queue
/// (not enough releasable file segments).
@ -211,7 +208,7 @@ void SLRUFileCachePriority::increasePriority(SLRUIterator & iterator, const Cach
if (size_to_free)
{
if (!probationary_queue.collectCandidatesForEviction(size_to_free, stat, eviction_candidates, {}, noop, {}, lock))
if (!probationary_queue.collectCandidatesForEviction(size_to_free, stat, eviction_candidates, {}, {}, lock))
{
/// "downgrade" candidates cannot be moved to probationary queue,
/// so entry cannot be moved to protected queue as well.
@ -220,7 +217,7 @@ void SLRUFileCachePriority::increasePriority(SLRUIterator & iterator, const Cach
return;
}
/// Make space for "downgrade" candidates.
eviction_candidates.evict(nullptr, lock);
eviction_candidates.evict();
}
/// All checks passed, now we can move downgrade candidates to
@ -294,10 +291,16 @@ size_t SLRUFileCachePriority::SLRUIterator::increasePriority(const CacheGuard::L
return getEntry()->hits;
}
void SLRUFileCachePriority::SLRUIterator::updateSize(int64_t size)
void SLRUFileCachePriority::SLRUIterator::incrementSize(size_t size, const CacheGuard::Lock & lock)
{
assertValid();
lru_iterator.updateSize(size);
lru_iterator.incrementSize(size, lock);
}
void SLRUFileCachePriority::SLRUIterator::decrementSize(size_t size)
{
assertValid();
lru_iterator.decrementSize(size);
}
void SLRUFileCachePriority::SLRUIterator::invalidate()

5
src/Interpreters/Cache/SLRUFileCachePriority.h
View File

@ -44,7 +44,6 @@ public:
FileCacheReserveStat & stat,
EvictionCandidates & res,
IFileCachePriority::IteratorPtr reservee,
FinalizeEvictionFunc & finalize_eviction_func,
const UserID & user_id,
const CacheGuard::Lock &) override;
@ -80,7 +79,9 @@ public:
void invalidate() override;
void updateSize(int64_t size) override;
void incrementSize(size_t size, const CacheGuard::Lock &) override;
void decrementSize(size_t size) override;
QueueEntryType getType() const override { return is_protected ? QueueEntryType::SLRU_Protected : QueueEntryType::SLRU_Probationary; }