JPS607303B2 - Page buffer search processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a data processing apparatus that manages page buffers on a storage device using a page buffer search processing method, particularly, for example, an LRU algorithm. The present invention relates to a page buffer search processing method that speeds up search processing for a page table by dividing the data into a plurality of sets and configuring and managing a chain for each set.

Conventionally, a storage device having a predetermined capacity, such as a page buffer in a data base, is managed according to an LRU algorithm.

That is, when the page buffer is accessed, the LRU priority of the page buffer is increased, and when the page buffer needs to be released, the LRU priority is increased.
The lowest priority page buffer is now freed. For this purpose, a page control table is created corresponding to each page buffer and points to the corresponding page buffer, and the pointer in the page control table is used to move other page control tables in the order according to the LRU priority. A structure that points to the following points is adopted. In order to increase the LRU priority, the pointer of the pointer in the page control table will be changed. be controlled. As mentioned above, LRU
Since each page buffer is chained according to priority, when a certain page buffer is specified and searched, a conventional method has been adopted in which the page control table is sequentially searched using a pointer according to the above-mentioned LRU priority. has been done.

For this, page. As the number of buffers increases, the time required for the above search process increases. The present invention
The aim is to solve this problem, and as mentioned above, L
The page control tables chained by the RU algorithm are divided into, for example, those with odd numbers and those with even numbers to form subdivisions, and a desired page buffer is extracted by chaining each set. , the purpose is to reduce the time required for the above search process.

Therefore, the page buffer search processing method of the present invention provides a plurality of page buffers on a storage device with a predetermined capacity, and transfers page information onto the page buffers before accessing. When it becomes necessary to execute processing while accessing the above page buffer and transfer new page information to the annotation storage device, the page with the lowest priority among the above multiple page buffers is - A data processing device having a page buffer update function that is controlled to release a buffer, allocate the new page information to the released page buffer, and then increase the priority of the page buffer. A page control table is provided corresponding to each of the page buffers and points to the corresponding page buffer, and a management table for managing the plurality of page control tables, each of the page control tables being , a priority chain pointer that points to another page control table according to a priority chain corresponding to the priority order between each of the above page buffers, and a priority chain pointer that points to another page control table according to a priority chain corresponding to the priority order between each of the above page buffers, and page buffers that make up the above priority chain according to a predetermined rule. Therefore, in addition to creating intra-group chain pointers corresponding to the ranks within the group divided into a plurality of groups, the above-mentioned management table ~ page control corresponding to the first page buffer of the above-mentioned priority chain It has a pointer that points to the table and a pointer that points to the page control table corresponding to the first page buffer of each set chain divided into the plurality of sets, and searches the page buffer of the above storage device. In doing so, the relevant page. The present invention is characterized in that the page control table is sequentially searched using a pointer corresponding to the group in the management table based on whether the buffer belongs to the above-mentioned and misaligned group. This will be explained below with reference to the drawings. The figure shows an embodiment of the invention.

Reference numbers 1-0, 1-2, . . . in the figure are respectively page buffers in which predetermined page information is stored;
2-0, 2-2, . . . are page control tables, which are provided for each page buffer and point to the address of the page buffer, and 3 is a management table. It represents the one that manages each page control table. In the case shown, the page
The address of buffer 1-0 is Bo, the address of page buffer 1-2 is &, the address of page control table 2-0 is Ao, and the address of page control table 2-2 is A2. and is shown as... Each page control table has a page buffer pointer, for example, page control table 2.
112 points to page buffer 12 by the contents of its pointer (B12). As stated at the beginning of this specification, the page buffer to which predetermined page information is transferred is managed according to the LRU algorithm.

To facilitate this, an LRU pointer is provided on each page control table. Now, as shown in the figure, if the LRU priorities are decreasing sequentially from the top in the figure, the address AII is written in the LRU pointer in table 2-12, and the LRU pointer in table 2-11 is written as address AII. Address A9 is written, and...
. . . The LRU pointer of table 2-10 has a description indicating the end. Also, in the management table 3, information on the number of page buffers chained by the LRU algorithm (in the case shown in the figure, ``10'') is stored.
) is written, and the LRU pointer points to the address A12 of the page control table 2-12, which corresponds to, for example, the page buffer 1-12 with the highest LRU priority at the present time.

Needless to say, under this condition, if it becomes necessary to release a page buffer, the page control table 2-10 corresponding to the page buffer 1-1 with the lowest LRU priority is extracted, The corresponding page buffer 1-10 is freed and new page information is transferred into that page buffer 1-10.

Then, the LRU priority of the page buffer-10 is set to be the highest. That is, for example, (i) the contents of the LRU pointer in the management table 3 are changed from AI2 to AI
(ii) Rewrite the contents of the LRU pointer in the page control table 2-10 from * shown in the figure to AI2,
(iii) The content of the LRU pointer in the page control table 2-8 is rewritten from AIO shown in the figure to *. Since management is performed using the LRU algorithm as described above, conventionally when a certain page buffer is specified and searched, the search is performed by sequentially following the LRU pointer.

That is, for example, when specifying and searching page buffers 1-7, the content AI2 of the LRU pointer in the management table 3
The page control table 2-12 is fetched based on the content of the LRU pointer of the table 2-12, and the page control table 2-11 is fetched based on the contents of the LRU pointer of the table 2-12.
, the desired page buffer 1-7 is extracted by fetching the page control table 2-7. For example, when specifying and searching page buffer 1-1 (not shown), after searching everything chained according to the contents of the upper tolerance RU pointer, page buffer 1-1 is searched on the chain. It was confirmed that it did not exist. Therefore, as the number of chained data buffers increases, the amount of search processing described above increases. In the case of the present invention, each data buffer chained by the above-mentioned LRU pointer is divided into N sets (N≧2), and a roughly corresponding pointer is created in the corresponding page control table. .

In the case shown, page buffer numbers #0, #1,...
. . . Corresponding to this, the data is divided into odd-numbered groups and even-numbered groups, and pointers are provided for each group. That is, in the case shown in the figure, the coarse pointer in the page control table 2-10 corresponding to the page buffer 1-1 belonging to the even number set contains the page control table corresponding to the next page buffer 1-8 belonging to the even number set. Address A8 of 2-8 is written.
Similarly, address A2 is written in the set pointer in page control table 2-8, and * indicating the end is written in the set pointer in page control table 2-12. Thus, an even-numbered chain is formed.
Furthermore, the coarse pointer in the page control table 2-5 corresponding to the page buffers 1-5 belonging to the odd-numbered group contains the address of the page control table 2-7 corresponding to the next page buffer 1-7 belonging to the odd-numbered group. A7 is written. The same goes for the rest, and an odd-numbered chain is formed. on the other hand,
In the management table 3, an even number set pointer pointing to the head of the even number set chain is created, and in the case shown in the figure, an address AIO is written. Similarly, an odd group pointer pointing to the beginning of the odd group chain is created, and in the case shown, address A5 is written therein. In the case of the present invention, as described above, for the page buffers belonging to the LRU chain, a thin chain using set pointers is further prepared.

Therefore, when searching by specifying page buffer 1-7, for example, the number of the page buffer 1-7 is checked to find out that it is an odd number set, and based on the content A5 of the odd number set pointer in the management table 3, Page control table 2
15, and the page control table 2-7 is fetched based on the content A7 of the set pointer in the table 2-5 to extract the page buffer 1-7. As a result, the amount of processing is reduced to 1/2 on average compared to the conventional method of following LRU pointers. Note that the process of checking the page number of the specified page buffer described above can also be done by software.
It can be determined by command. As described above, according to the present invention, the search processing time when a page buffer is specified is shortened. The search process is an essential process in a system having a database, and reducing the processing time greatly improves the efficiency of the entire system.

[Brief explanation of the drawing]

The figure shows the configuration of an embodiment of the present invention. In the figure, 1-0, 1-2, . . . are page buffers, 2-0, 2-2, . . . are page control tables, respectively.
3 represents a management table.

Claims (1)

[Claims] 1. Provide multiple page buffers on a storage device with a predetermined capacity, transfer page information onto the page buffers, and execute processing while accessing the page buffers when accessing. However, when it becomes necessary to transfer new page information to the storage device, the page buffer with the lowest priority among the plurality of page buffers is released and the new page information is transferred. In a data processing device that has a page buffer update function that allocates the page buffer to the released page buffer and increases the priority of the page buffer, A page control table that points to a corresponding page buffer and a management table that manages the plurality of page control tables are provided, and each page control table is arranged in a priority chain corresponding to the priority order among the page buffers. Therefore, priority chain pointers that point to other page control tables and page buffers that make up the priority chain are divided into a plurality of groups according to predetermined rules, and the priority chain pointers are arranged to correspond to the ranking within the group. In addition, the management table has a pointer pointing to a page control table corresponding to the first page buffer of the priority chain, and a pointer for each group chain divided into the plurality of groups. A pointer pointing to the page control table corresponding to the first page buffer is created, and when searching for a page buffer on the storage device, it is determined which of the above groups the page buffer belongs to. The page buffer search processing method is characterized in that the page control table is sequentially searched based on the pointer corresponding to the group in the management table.