Negotiating Transmit Wake Time for Power Savings
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Solution Overview
Problem
Modern computer systems face challenges in balancing power savings with wake latency during periods of reduced network activity, as deeper power saving modes require longer sleep durations, which can lead to increased wake times and power consumption inefficiencies.
Innovation Solution
The technique involves negotiating a 'transmit wake time' (Tw system) between link partners, where a transmitting link partner delays data transmission after sending wake symbols, allowing the receiving partner to enter a deeper power saving state, by buffering data and using flow control messages to extend the wake time, thus reducing system power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the system enters deeper power saving modes to reduce power consumption, then power savings increase, but wake latency increases
Solution Approach 1:
The transmitting link partner sends wake symbols in advance before the actual data transmission. This preliminary action allows the receiving link partner to start its wake-up sequence earlier, reducing the effective wake latency experienced when data needs to be received, while still allowing the system to spend extended time in deeper power saving modes.
Solution Approach 2:
The system dynamically negotiates the transmit wake time parameter between link partners, allowing the wake latency to be adjusted based on the receiving partner's power saving mode requirements. This dynamic adjustment enables the system to optimize between power savings and wake latency in real-time based on traffic patterns and power state requirements.
2Use of energy by moving object
If the system extends sleep duration to enter deeper power modes, then power savings increase, but the risk of data loss increases
Solution Approach 1:
By sending wake symbols as a preliminary notification before data transmission, the receiving link partner can begin its wake-up process in advance. This ensures that even after extended sleep periods in deeper power modes, the system is ready to receive data when the wake symbols are sent, preventing data loss while maintaining long sleep durations for power savings.
Solution Approach 2:
The negotiation mechanism provides feedback between link partners about their power saving capabilities and requirements. The receiving partner communicates its needs for extended wake time to enter deeper power modes, and the transmitting partner adjusts its transmission timing accordingly, ensuring reliable data delivery while maximizing power savings.
Data Source
AI summary
Includes receiving, from a link partner, a message specifying a link partner receive wake time and resolving to a transmit wake time.