Hybrid memory management

A system comprising:

• one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising:
• determining, with a processor, whether an access bit is set for each page table entry of a page table based on a scan of the page table with a page table scanner, the access bit indicating whether a page associated with the page table entry was accessed in a last scan period;
• incrementing a count for each page in response to determining that the access bit for the page table entry associated with the page indicates that the page associated with the page table entry was not accessed in the last scan period, wherein the count for each page indicates the number of consecutive previous scan periods that the page was not accessed ending at the last scan period and the count for a particular page is greater than one;
• after determining, with the processor, whether the access bit is set for each page table entry, resetting the access bit of each of the pages that were accessed;
• receiving a request to access, from a main memory, a first page of data;
• initiating a page fault based on determining that the first page of data is not stored in the main memory;
• and
• in response to initiating the page fault, determining a particular page based on the count for each page and transferring the first page of data from the secondary memory to the main memory at the location of the released particular page.

A non-transitory computer-readable medium storing software comprising instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising:

• determining, with a processor, whether an access bit is set for each page table entry of a page table based on a scan of the page table with a page table scanner, the access bit indicating whether a page associated with the page table entry was accessed in a last scan period;
• incrementing a count for each page in response to determining that the access bit for the page table entry associated with the page indicates that the page associated with the page table entry was not accessed in the last scan period, wherein the count for each page indicates the number of consecutive previous scan periods that the page was not accessed ending at the last scan period and the count for a particular page is greater than one;
• after determining, with the processor, whether the access bit is set for each page table entry, resetting the access bit of each of the pages that were accessed;
• receiving a request to access, from a main memory, a first page of data;
• initiating a page fault based on determining that the first page of data is not stored in the main memory;
• and
• in response to initiating the page fault, determining a particular page based on the count for each page and transferring the first page of data from the secondary memory to the main memory at the location of the released particular page.