CPU Timestamp Generation via Successive Time Function Calls
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Solution Overview
Problem
Existing timekeeping methods on computing devices suffer from unpredictable execution due to processor sleep states, resulting in low-resolution timestamps that are not accurate enough for applications requiring precision within one to two microseconds, such as cloud computing and industrial systems.
Innovation Solution
Implementing two successive calls to a time function that loads instructions into the processor pipeline and caches data, with the initial call optimizing instruction execution and the subsequent call executing predictably without entering a sleep state, thereby ensuring high-resolution timestamp generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the processor enters a sleep state to save power, then energy consumption is reduced, but timestamp accuracy deteriorates due to unpredictable execution delays
Solution Approach 1:
The patent applies preliminary action by performing a first call to the time function before the second call. This first call primes the processor pipeline and caches instructions and data, ensuring that when the second call occurs, the processor can execute quickly without entering a sleep state. This preliminary priming action eliminates the unpredictability of sleep state transitions while maintaining power efficiency.
Solution Approach 2:
The patent uses the processor pipeline and instruction cache as intermediaries. The first call to the time function loads instructions into the pipeline and caches associated data, creating an intermediary prepared state. When the second call occurs, these intermediaries are already in place, allowing deterministic execution without sleep state transitions, thus ensuring high-resolution timestamps.
2Use of energy by stationary object
If conventional time functions are used with processor sleep states, then power-saving measures are achieved, but time resolution deteriorates to low resolution
Solution Approach 1:
The first call to the time function serves as a preliminary action that prepares the processor by loading instructions into the pipeline and caching data. This ensures that the subsequent second call can execute deterministically without entering sleep states, achieving both power-saving capability (by avoiding frequent sleep transitions) and high time resolution (through predictable execution).
Solution Approach 2:
The patent maintains continuity of useful action by keeping the processor in a working state through the use of successive time function calls. The first call primes the system, and the second call executes with predictable timing, ensuring continuous high-resolution timekeeping without the interruptions and delays associated with sleep state transitions.
3Productivity
If the processor optimizes initial function call execution through prediction, then initial call performance is improved, but subsequent call predictability worsens due to sleep state transitions
Solution Approach 1:
The first call to the time function is deliberately used as a preliminary action to prime the processor pipeline and cache instructions and data. Although this initial call may have variable execution time due to optimization and prediction activities, it sets up the system so that the second call executes predictably without sleep state transitions, ensuring reliable timing for the actual timestamp measurement.
Data Source
AI summary
Timekeeping on a computing device is deterministically performed by implementing two successive calls to a time function that returns current time based on a continuously running counter that is maintained in one or more cores of the device's CPU. The same fixed time computation parameters are used in each call, with the single variable being a value that is read from the counter. For the initial call to the time function, the processor optimizes the instruction execution by predicting the function's execution path based on observed patterns. As the instructions and data are already cached, and the processor has the results of the prior execution path prediction, the subsequent call executes quickly and predictably relative to the initial call while the processor remains in a working (i.e., non-sleep) state. The series of calls provides a deterministic time computation with improved accuracy by mitigating the unpredictability of processor sleep state delays.