Dynamically adjusted threshold for population of secondary cache

• US 8,972,662 B2
• Filed: 04/26/2012
• Issued: 03/03/2015
• Est. Priority Date: 10/31/2011
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Benhase, Michael T., Blinick, Stephen L., Eleftheriou, Evangelos S., Gupta, Lokesh M., Haas, Robert, Hu, Xiao-Yu, Koltsidas, Ioannis, Pletka, Roman A.
• Primary Examiner(s): Sadler, Nathan
• Application Number:
  US13/457,290
• Publication Number:
  US 20130111131A1
• Time in Patent Office: 1,041 Days
• Field of Search: None
• US Class Current: 711/122
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 12/0888 using selective caching, e.g. bypass
• CPC Class Codes: G06F 12/0897 with two or more cache hierarchy levels with multilevel cache hierarchies G06F12/0811
• CPC Class Codes: G06F 2212/225 Hybrid cache memory, e.g. having both volatile and non-volatile portions

Abstract

The population of data to be inserted into secondary data storage cache is controlled by determining a heat metric of candidate data; adjusting a heat metric threshold; rejecting candidate data provided to the secondary data storage cache whose heat metric is less than the threshold; and admitting candidate data whose heat metric is equal to or greater than the heat metric threshold. The adjustment of the heat metric threshold is determined by comparing a reference metric related to hits of data most recently inserted into the secondary data storage cache, to a reference metric related to hits of data most recently evicted from the secondary data storage cache; if the most recently inserted reference metric is greater than the most recently evicted reference metric, decrementing the threshold; and if the most recently inserted reference metric is less than the most recently evicted reference metric, incrementing the threshold.

Claims

1. A method for populating data into a secondary data storage cache of a computer-implemented cache data storage system, comprising:

determining a heat metric of candidate data to be inserted into said secondary data storage cache;

rejecting candidate data provided to said secondary data storage cache whose heat metric is less than a heat metric threshold;

admitting to said secondary data storage cache, candidate data provided to said secondary data storage cache whose heat metric is equal to or greater than said heat metric threshold; and

adjusting said heat metric threshold in accordance with caching efficiency of a present state of said secondary data storage cache, comprising;

maintaining a reference metric related to hits of data most recently inserted into said secondary data storage cache;

maintaining a reference metric related to hits of data most recently evicted from said secondary data storage cache;

comparing said reference metric of said most recently inserted data to said reference metric of said most recently evicted data;

if said most recently inserted reference metric is greater than said most recently evicted reference metric, decrementing said heat metric threshold; and

if said most recently inserted reference metric is less than said most recently evicted reference metric, incrementing said heat metric threshold.

2. The method of claim 1, wherein said cache data storage system additionally comprises a first data storage cache and wherein said heat metric is based on the heat of said data while said data was stored in said first data storage cache of said cache data storage system.

3. The method of claim 2, wherein said data provided to said secondary data storage cache comprises data demoted from said first data storage cache.

4. The method of claim 3, wherein said most recently inserted data is listed in an MRI list and said most recently evicted data is listed in an MRE list, and said reference metric comprises counting hits in said secondary data storage cache for said data listed in said MRI while said data is in said secondary data storage cache and hits for said data listed in said MRE after said data has been evicted from said secondary data storage cache.

5. The method of claim 4, wherein said data comprise pages of data and counting hits for said heat metric is determined on a per page basis, and said most recently inserted and said most recently evicted reference metrics are determined for all of said pages listed respectively in said MRI and said MRE.

6. The method of claim 1, wherein said adjusting step additionally comprises, if said most recently inserted reference metric and said most recently evicted reference metric are substantially the same, said heat metric threshold is left unchanged.