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Published byJoanna Freeman Modified over 6 years ago
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Effective mechanism for bufferless networks at intensive workloads
Rachata Ausavarungnirun, Kevin Chang
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Problems (recap) Bufferless deflection flow control only performs well under light workloads Real applications contain a mixture of light and heavy workloads Latency and energy consumption increase significantly when there are several heavy workloads
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Possible Solution Changing topologies Throttling the injection
Adding more links so flits can reach the destination sooner (Flattened butterfly) Increases the total network capacity Throttling the injection Be aware of the workload characteristics Prioritizing latency critical workloads over non latency critical workloads
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Key Idea (Topology) Imposing a new topology that allows bufferless to be able to tolerate high intensity workloads BLESS networks with Flattened Butterfly can outperform buffered networks on a mesh (see results in the future slide) Require a good router design to efficiently operate the new topology The number of ports needed in Flattened butterfly scale as 2*SQRT(N)
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FBFLY result
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FBFLY disadvantages The number of port in each router increases by 2*sqrt(total nodes) This will increase the size of the router (crossbar, datapath, etc.) This increases the latency in the router Conclusion: FBFLY does not scale well with a large network
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Throttling Problem Goal Solution
Network intensive applications contend for the shared resource with less intensive applications which are more critical Goal Reduce interference to increase system throughput Solution Prevent network intensive applications from injecting packets to avoid saturating the network
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Throttling Key Ideas When the network is approaching the saturation point, start throttling Completely shut off the injection of intensive applications for some time intervals Reduce interference from intensive applications Guarantee of Fairness Allow network intensive applications to inject once in a while
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Throttling Who? Applications with high L1 MPKI (misses per K instructions) An application with high L1 MPKI injects a large amount of packets Applications with high L1 MPKI are less sensitive to latency
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Throttling (When?) Interval-based throttling
If totalMPKI < static threshold Free for all state, any node can inject flits Timeline FFA
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Throttling (When?) If totalMPKI > static threshold
Start throttling high intensive applications Application with low MPKI can inject freely at any intervals Allow one application with high MPKI to run in each interval in a round robin manner Fine grain intervals Timeline FFA App1 App2 App1 App2
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Throttling (When?) If totalMPKI > static threshold
Start throttling high intensive applications Application with low MPKI can inject freely at any intervals Allow one application with high MPKI to run in each interval in a round robin manner Fine grain intervals Timeline FFA App1 App2 App1 App2
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Throttling (When?) If totalMPKI > static threshold
Start throttling high intensive applications Application with low MPKI can inject freely at any intervals Allow one application with high MPKI to run in each interval in a round robin manner Fine grain intervals Timeline FFA App1 App2 App1 App2
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Throttling (When?) If totalMPKI > static threshold
Start throttling high intensive applications Application with low MPKI can inject freely at any intervals Allow one application with high MPKI to run in each interval in a round robin manner Fine grain intervals Timeline FFA App1 App2 App1 App2
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Throttling (When?) Termination If totalMPKI < static_threshold_low
Termination point Timeline … … … Last App FFA
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Questions?
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Backup Slides
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Throttling policy MPKI 2 10 40 1 15 53 4 8 45 Current MPKI Threshold
Throttle mode? 178 200 N
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Throttling policy MPKI 3 10 63 2 15 76 8 73 Current MPKI Threshold
Throttle mode? 252 200 Y
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Throttling Mode: Period 1
MPKI 3 10 63 2 15 76 4 8 73 Current MPKI Threshold Throttle mode? 252 200 N
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Throttling Mode: Period 2
MPKI 3 10 63 2 15 76 4 8 73 Current MPKI Threshold Throttle mode? 252 200 N
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Throttling Mode: Period 3
MPKI 3 10 63 2 15 76 4 8 73 Current MPKI Threshold Throttle mode? 252 200 N
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Throttling Mode: Period 4
SlowDown 4.4 3.6 1.4 4.8 2.4 1.3 3.4 2.7 1.5 Injection Rate Threshold Throttle mode? low 4 Y
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Throttling Mode SlowDown (updated) 2.7 1.2 1.8 3.2 1.1 1.5 1.4 2.3 1.7
Injection Rate Threshold Throttle mode? low 4 N
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