Selective Cache Fills for Write Misses Using Stack Pointer Analysis
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Solution Overview
Problem
Cache memory write operations are stalled due to unnecessary cache fills, where fetched cache lines may contain data no longer referenced by the program, leading to inefficiencies and back pressure in the system.
Innovation Solution
Implement a method where cache fills in response to write misses are selectively performed based on the stack pointer, determining whether the address is between the previous and current stack pointer values and checking the write history indicator, allowing writes to proceed without a cache fill if the address is within the recently allocated memory space and the write history indicator is set.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a write-allocate policy is implemented in cache memory, then write operations can be performed after cache fill, but write operations are stalled during cache fill and read bandwidth is consumed unnecessarily
Solution Approach 1:
The patent changes the parameter of cache fill behavior by introducing a selective write-allocate policy that differs from the traditional uniform approach. The cache controller examines the address being written and determines whether to perform a cache fill based on specific conditions (write miss status and address characteristics), thereby changing the operational parameters of the cache system to avoid unnecessary stalls and read bandwidth consumption while maintaining reliable write operation completion
2Reliability
If cache fills are performed for all write misses, then cache data is ensured to be present, but unnecessary read bandwidth is consumed and system back pressure increases
Solution Approach 1:
The patent extracts the unnecessary cache fill operations from the standard write-allocate process by introducing a selection mechanism. The cache controller identifies and removes (skips) cache fills for addresses that are determined not to need them (based on write miss status and address analysis), thereby taking out the harmful element of unnecessary read bandwidth consumption while preserving cache data availability for addresses that actually require it
Solution Approach 2:
The patent applies local quality by treating different addresses differently in the write-allocate process. Instead of uniformly performing cache fills for all write misses, the cache controller analyzes individual address characteristics and applies cache fill operations only where necessary, creating a localized, address-specific quality of service that reduces overall read bandwidth consumption while maintaining data availability where needed
Data Source
AI summary
A cache memory receives a request to perform a write operation. The request specifies an address. A first determination is made that the cache memory does not include a cache line corresponding to the address. A second determination is made that the address is between a previous value of a stack pointer and a current value of the stack pointer. A third determination is made that a write history indicator is set to a specified value. The write operation is performed in the cache memory without waiting for a cache fill corresponding to the address to be performed, in response to the first, second, and third determinations.