Deduplication-aware page cache

摘要

An access request that includes a combination of a file identifier and an offset value is received. If the page cache does not contain the page indexed by the combination, then the file system is accessed and the offset value is mapped to a disk location. The file system can access a block map to identify the location. A table (e.g., a shared location table) that includes entries (e.g., locations) for pages that are shared by multiple files is accessed. If the aforementioned disk location is in the table, then the requested page is in the page cache and it is not necessary to add the page to the page cache. Otherwise, the page is added to the page cache.

主权项

1. A non-transitory computer-readable storage medium having computer-executable instructions for causing a computer system to perform a method comprising:
receiving an access request comprising a combination of a file identifier for a file and an offset value; determining whether a page cache contains a page of data indexed by said combination and, if not, then:
accessing a file system to map said offset value to an on-disk location;determining whether said location is in a table comprising locations for pages that are shared by multiple files and that are in said page cache;if said location is in said table, then responding to said access request without adding said page to said page cache; andif said location is not in said table, then adding said page to said page cache and responding to said access request; wherein, if said page is write protected, then:
generating a page fault in response to an attempt to write to said page;making a copy of said page;causing a page descriptor of a file for which said write was attempted to point to said copy; andremoving said page descriptor of said file for which said write was attempted from a list associated with said location.