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Dedicate cacheline for DB mutex #9637

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Dedicate cacheline for DB mutex #9637

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3a3dce9
Dedicate cacheline for DB mutex
ajkr Feb 26, 2022
7578d1c
pad also at end
ajkr Feb 26, 2022
8538f8b
fix
ajkr Feb 26, 2022
52c8dee
use CacheAlignedInstrumentedMutex
ajkr Feb 27, 2022
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5 changes: 4 additions & 1 deletion db/db_impl/db_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1187,7 +1187,10 @@ class DBImpl : public DB {
// WriteToWAL need different synchronization: log_empty_, alive_log_files_,
// logs_, logfile_number_. Refer to the definition of each variable below for
// more description.
mutable InstrumentedMutex mutex_;
//
// `mutex_` can be a hot lock in some workloads, so it deserves dedicated
// cachelines.
mutable CacheAlignedInstrumentedMutex mutex_;

ColumnFamilyHandleImpl* default_cf_handle_;
InternalStats* default_cf_internal_stats_;
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8 changes: 8 additions & 0 deletions monitoring/instrumented_mutex.h
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,14 @@ class InstrumentedMutex {
int stats_code_;
};

class ALIGN_AS(CACHE_LINE_SIZE) CacheAlignedInstrumentedMutex
: public InstrumentedMutex {
using InstrumentedMutex::InstrumentedMutex;
char padding[(CACHE_LINE_SIZE - sizeof(InstrumentedMutex) % CACHE_LINE_SIZE) %
CACHE_LINE_SIZE] ROCKSDB_FIELD_UNUSED;
};
static_assert(sizeof(CacheAlignedInstrumentedMutex) % CACHE_LINE_SIZE == 0);

// RAII wrapper for InstrumentedMutex
class InstrumentedMutexLock {
public:
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