Details
Description
Run this script:
#!/bin/bash
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THREADS=$1
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CMD=$2
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if [ "$3" == "" ]; then
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BENCH_SECONDS=10
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else
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BENCH_SECONDS="$3"
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fi
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mongo --quiet -eval 'db.foo.insert({_id:1})'
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if [ $CMD == "false" ]; then
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mongo --quiet -eval '
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ops = [{op:"find", ns:"test.foo", query: {_id: 1}}]
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results = benchRun({ops:ops, parallel:'$THREADS', seconds:'$BENCH_SECONDS'})
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print(Math.round(results["totalOps/s"]))
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'
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else
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mongo --quiet -eval '
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ops = [{op:"command", command: {"find": "foo", "filter": {"_id" : 1}}, ns:"test"}]
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results = benchRun({ops:ops, parallel:'$THREADS', seconds:'$BENCH_SECONDS'})
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print(Math.round(results["totalOps/s"]))
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'
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fi
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You get much more lock contention with the command path vs not:
benchRun.find 32 false 30
233511 ops/s
- 6.32% mongod [kernel.kallsyms] [k] _raw_spin_lock
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- _raw_spin_lock
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- 48.54% futex_wake
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do_futex
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sys_futex
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system_call_fastpath
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- __lll_unlock_wake
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+ 41.15% mongo::PlanExecutor::registerExec()
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+ 35.88% mongo::PlanExecutor::deregisterExec()
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+ 5.40% mongo::runQuery(mongo::OperationContext*, mongo::QueryMessage&, mongo::Namesp
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+ 5.26% mongo::AutoGetCollection::AutoGetCollection(mongo::OperationContext*, mongo::
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+ 4.98% mongo::AutoGetCollectionForRead::~AutoGetCollectionForRead()
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+ 2.61% mongo::getExecutorFind(mongo::OperationContext*, mongo::Collection*, mongo::N
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+ 1.92% mongo::WiredTigerCursor::WiredTigerCursor(std::string const&, unsigned long,
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+ 1.72% mongo::WiredTigerRecoveryUnit::~WiredTigerRecoveryUnit()
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+ 1.09% mongo::fillOutPlannerParams(mongo::OperationContext*, mongo::Collection*, mon
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+ 30.15% futex_wait_setup
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+ 18.51% try_to_wake_up
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vs:
benchRun.find 32 true 30
119839 ops/s
- 43.11% mongod [kernel.kallsyms] [k] _raw_spin_lock
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- _raw_spin_lock
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- 51.98% futex_wake
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do_futex
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sys_futex
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system_call_fastpath
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- __lll_unlock_wake
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+ 23.98% mongo::ClientCursor::ClientCursor(mongo::CursorManager*, mongo::PlanExecutor
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+ 20.36% mongo::ClientCursorPin::deleteUnderlying()
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+ 19.67% mongo::PlanExecutor::registerExec()
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+ 18.84% mongo::PlanExecutor::deregisterExec()
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+ 16.71% mongo::ClientCursorPin::ClientCursorPin(mongo::CursorManager*, long long)
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- 45.15% futex_wait_setup
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futex_wait
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do_futex
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sys_futex
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system_call_fastpath
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- __lll_lock_wait
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+ 22.64% mongo::ClientCursor::ClientCursor(mongo::CursorManager*, mongo::PlanExecutor
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+ 22.05% mongo::PlanExecutor::deregisterExec()
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+ 19.39% mongo::PlanExecutor::registerExec()
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+ 18.94% mongo::ClientCursorPin::deleteUnderlying()
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+ 16.70% mongo::ClientCursorPin::ClientCursorPin(mongo::CursorManager*, long long)
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+ 2.56% try_to_wake_up
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Contention appears to be CursorManager::_mutex.
Attachments
Issue Links
- is related to
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SERVER-20596 Performance regression in new mongos query path (about 17% worse than 3.0)
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- Closed
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