EP0230354A2
Expired / Lapsed
EP
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Enhanced handling of large virtual storage extents
Assignee: International Business Machines Corp
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Filing: 1987-01-08
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Granted: —
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Expires: 2007-01-08
Abstract
Abstract In a virtual memory data processing system, the use of a pageable External Page Table data structure for recording current status and disk address information for each virtual page in the system and a non-pageable or pinned table of tables, provides improved system performance when a large number of virtual pages are to be operated on in the same manner. As disclosed, each page of External Page Table entries can record a predetermined number of entries (512), depending on the byte capacity of each virtual page (2,048) and the size of each entry (4 bytes). One page of 512 entries corresponds to 1 megabyte of virtual storage (512 × 2,048) and also appears as one entry in a pinned External Page Table. The pinned External Page Table is referred to as the "XPT of the XPT," and has the same format as the pageable XPT. A 256 megabyte segment of virtual memory is representable in the XPT of the XPT by 256, 4 byte entries, or one-half of a page. Where all virtual pages represented by a page of XPT entries are to be processed in the same way (i.e., created, destroyed), one operation on one entry in the XPT of the XPT is made, rather than 512 operations on the 512 entries of the XPT.
Inventors
- 👤 Mark Douglas Rogers
- 👤 John Thomas O'quinn Ii
- 👤 John Claude O'quinn Ii
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 05:08
CPC Classifications
G; G06; G06F; G06F12/00; G06F12/02; G06F12/08; G06F12/10; G06F12/1009
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
137 words
A method of enhancing the handling of large virtual storage extents in a virtual memory data processing system including employing an External Page Table (XPT) having a plurality of entry positions, each of which relates one virtual page address to an address in real memory where information associated with the one virtual page is physically stored, in order to access selected data, establishing a non-pageable data structure (XPT²) having a format similar to the XPT in which each separate entry position corresponds to a different pageable External Page Table in order to access the appropriate External Page Table in order to access selected data, and modifying only the appropriate entry in the non-pageable data structure (XPT²) to indicate the same change to the status of each page represented by the entries in the associated External Page Table.
Claim 2
Independent Claim
137 words
A method of enhancing the handling of large virtual storage extents in a virtual memory data processing system including employing an External Page Table (XPT) having a plurality of entry positions, each of which relates one virtual page address to an address in real memory where information associated with the one virtual page is physically stored, in order to access selected data, establishing a non-pageable data structure (XPT²) having a format similar to the XPT in which each separate entry position corresponds to a different pageable External Page Table in order to access the appropriate External Page Table in order to access selected data, and modifying only the appropriate entry in the non-pageable data structure (XPT²) to indicate the same change to the status of each page represented by the entries in the associated External Page Table.
Claim 3
Dependent Claim
68 words
A method as claimed in Claim 1 in which each the entry position includes "n" bytes and the step of modifying an entry in the non-pageable data structure is in response to the system requesting a segment of the virtual memory to be created and which the number of pages to be created in the segment exceeds x/n, where "x" equals the byte capacity of each virtual page.
Claim 4
Dependent Claim
28 words
A method as claimed in Claim 2 in which the "n" byte entry position includes a page status field for indicating the current status of the associated page.
Claim 5
Dependent Claim
34 words
A method as claimed in Claim 3 in which each External Page Table includes 512 entries corresponding to 512 virtual pages and each virtual page is capable of storing 2K (2,048) bytes of data.
Claim 6
Dependent Claim
51 words
A method as claimed in Claim 2, further including determining the number of pages that the system has requested to be created, and modifying the entry in the non-pageable data structure only when all of the entries in the related External Page Table are to be modified in the same way.
Claim 7
Dependent Claim
43 words
A method as claimed in Claim 5, further including allocating at least one pageable External Page Table corresponding in size to one page of virtual memory and at least one non-pageable External Page Table for every x/n or less pages of XPT entries.
Claim 8
Dependent Claim
65 words
A method as claimed in Claim 2, further including subsequently increasing the number of virtual pages in the the segment after it has been created, allocating a second non-pageable data structure, swapping entries from the first non-pageable data structure with entries in the second non-pageable data structure for all complete pages of XPT entries, and copying old XPT entries into the second non-pageable data structure.
Claim 9
Dependent Claim
35 words
A method as claimed in Claim 7, further including modifying the old XPT entries subsequent to copying them into the second non-pageable data structure to define the status of each corresponding page as being unreferenced.
Claim 10
Dependent Claim
67 words
A method as claimed in Claim 2, further including copying the created segment of memory to another segment of memory when the created segment is storing a sparse field of information and includes a "hole" having at least x/n contiguous non-referenced pages, but without, during such operation, copying any virtual pages that an entry in the non-pageable data structure indicates is a "hole" of unreferenced virtual pages.
Claim 11
Dependent Claim
65 words
A method as claimed in Claim 2, further including, when subsequently destroying the created segment of virtual memory, checking each entry in the External Page Table to determine the status of the corresponding virtual pages prior to performing an operation that releases the page, unless a prior check of the appropriate portion of the non-pageable data has indicated that all corresponding x/n pages are unreferenced.
Claim 12
Dependent Claim
156 words
A virtual memory data processing system adapted for the enhanced handling of large virtual storage extents, including means for maintaining an External Page Table (XPT) having a plurality of entry positions, each of which relates one virtual page address to an address in real memory where information associated with the one virtual page is physically stored and used to access selected data identified by a running process by its virtual address, and means for establishing a non-pageable or pinned data structure (XPT) having a format similar to the XPT in which each separate entry position corresponds to a different pageable External Page Table in order to access the appropriate External Page Table on the way to accessing selected data, the system being arranged to modify only the appropriate entry in the non-pageable data structure (XPT²) to indicate the same change to the status of each page represented by the entries in the associated External Page Table.
Claim 13
Dependent Claim
156 words
A virtual memory data processing system adapted for the enhanced handling of large virtual storage extents, including means for maintaining an External Page Table (XPT) having a plurality of entry positions, each of which relates one virtual page address to an address in real memory where information associated with the one virtual page is physically stored and used to access selected data identified by a running process by its virtual address, and means for establishing a non-pageable or pinned data structure (XPT) having a format similar to the XPT in which each separate entry position corresponds to a different pageable External Page Table in order to access the appropriate External Page Table on the way to accessing selected data, the system being arranged to modify only the appropriate entry in the non-pageable data structure (XPT²) to indicate the same change to the status of each page represented by the entries in the associated External Page Table.
References Cited (Backward Citations)
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