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MCOL-5044 This patch replaces PriorityThreadPool with FairThreadPool that uses a simple

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operations + morsel size weight model to equally allocate CPU b/w parallel query morsels.
This patch delivers better parallel query timings distribution(timings graph resembles normal
distribution with a bigger left side thus more queries runs faster comparing with PrioThreadPool-based
single-node installation).
See changes in batchprimitiveprocessor-jl.h and comments in fair_threadpool.h for
important implementation details
This commit is contained in:
Roman Nozdrin
2022-05-24 17:57:40 +00:00
committed by Roman Nozdrin
parent 0f0b3a2bed
commit fd8ba33f21
12 changed files with 173 additions and 254 deletions
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26
utils/threadpool/fair_threadpool.h
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@ -39,6 +39,12 @@
namespace threadpool
{
// The idea of this thread pool is to run morsel jobs(primitive job) is to equaly distribute CPU time
// b/w multiple parallel queries(thread maps morsel to query using txnId). Query(txnId) has its weight
// stored in PriorityQueue that thread increases before run another morsel for the query. When query is
// done(ThreadPoolJobsList is empty) it is removed from PQ and the Map(txn to ThreadPoolJobsList).
// I tested multiple morsels per one loop iteration in ::threadFcn. This approach reduces CPU consumption
// and increases query timings.
class FairThreadPool
{
public:
@ -92,23 +98,6 @@ class FairThreadPool
*/
void dump();
// If a job is blocked, we want to temporarily increase the number of threads managed by the pool
// A problem can occur if all threads are running long or blocked for a single query. Other
// queries won't get serviced, even though there are cpu cycles available.
// These calls are currently protected by respondLock in sendThread(). If you call from other
// places, you need to consider atomicity.
void incBlockedThreads()
{
blockedThreads++;
}
void decBlockedThreads()
{
blockedThreads--;
}
uint32_t blockedThreadCount() const
{
return blockedThreads;
}
size_t queueSize() const
{
return weightedTxnsQueue_.size();
@ -165,9 +154,6 @@ class FairThreadPool
using Txn2ThreadPoolJobsListMap = std::unordered_map<TransactionIdxT, ThreadPoolJobsList*>;
Txn2ThreadPoolJobsListMap txn2JobsListMap_;
WeightedTxnPrioQueue weightedTxnsQueue_;
std::atomic<uint32_t> blockedThreads;
std::atomic<uint32_t> extraThreads;
bool stopExtra;
};
} // namespace threadpool