Abstract: In a storage system that implements metadata paging, the page free pool is replenished in the background to reduce foreground evictions and associated latency on page-in. A two-level page eviction controller with cascaded proportional, integral, derivative (PID) controllers optimizes the size of the free page pool and optimizes the rate at which pages are freed in the background. By optimizing these two parameters the page eviction controller dynamically maximizes used pages (minimizing free pages) to increase the metadata cache hit ratio. Optimizing the parameters also reduces the chances of foreground page evictions, thereby reducing IO latency, during both steady state and burst page-in requests.

Abstract: In a storage system that implements metadata paging, the page free pool is replenished in the background to reduce foreground evictions and associated latency on page-in. A two-level page eviction controller with cascaded proportional, integral, derivative (PID) controllers optimizes the size of the free page pool and optimizes the rate at which pages are freed in the background. By optimizing these two parameters the page eviction controller dynamically maximizes used pages (minimizing free pages) to increase the metadata cache hit ratio. Optimizing the parameters also reduces the chances of foreground page evictions, thereby reducing IO latency, during both steady state and burst page-in requests.