JPH0644248B2 - Cache memory positioning system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The specified sector value of the magnetic disk is given to the disk cache of the magnetic disk, and when the address position on the disk cache corresponding to this is obtained, it was obtained at the time of the previous access. By using the information that is a set of the sector value and the address corresponding to it, by determining the address of the record that is the starting point of the address calculation of this time according to the large or small relation between the specified sector value of this time and the previous sector value ， Reduce the address positioning time.

[Industrial application field]

The present invention relates to a disk cache of a magnetic disk used in a computer, and more particularly to a cache memory positioning method corresponding to a sector value.

[Conventional technology]

The recording state of a certain track on the conventional magnetic disk of the variable length recording format and the storage state on the disk cache memory corresponding to that track are shown in FIGS.

In FIG. 4 (a), the track of the magnetic disk is divided into sectors of a constant area (word length) starting from the index mark position, each sector is given a sector value (number), and the track is Following the home address part HA,
Records R0 and R composed of a count part C and a data part D
1, R2 ... Are recorded.

As shown in FIG. 4 (a), since the data length is variable according to the variable length recording format, the position of each record is not uniquely determined with respect to the sector value.

On the other hand, as shown in FIG. 4 (b), the storage state of the memory of the disk cache corresponding to the tracks of this magnetic disk has a recording gap G (Fig. 4 (a)) that is always provided in recording on the magnetic disk. Are deleted and each record is sequentially stored at consecutive address positions in memory without any gap.

There is a Set Sector command as an access from the CPU to the record of the track recorded in the disk cache memory.

This command is given by designating a sector value on a specific track of the magnetic disk, and when executing this command in the conventional disk cache control device, the head address (HA Memory location) is obtained from a table or the like, the memory address corresponding to the designated sector value is obtained from the start address and the start sector value 0.

Therefore, conventionally, when the memory at the address position after the fixed word length (word length of HA) is read from the start position address of the memory, as shown in FIG.
Since there is a count section of 0 and the data length of the record is included in a part of the content, the memory address of the record R1 is obtained next.

When the sector value designated by the set sector command is m, each recording unit H from the start position of the memory address
The sum of the word lengths of A, R0-C, R0-D, R1-C, R1-D, ... And the word length of the gap G between the recording parts is added,
This is divided by the word length specific to one sector to convert it to a sector value, and if the result is smaller than m, the memory address of the next record (the memory address of the previous record is added to the count part of this record) The cache memory is read out by adding the data length of), and the data length and the gap length are added to convert into a sector value, and m
When the value is equal to or larger than m, the address corresponding to the specified sector value is obtained as the memory address at that time, and the positioning is completed.

[Problems to be solved by the invention]

As described above, according to the conventional address positioning method for the specified sector value, it is necessary to reach the specified sector value while tracing each record in order from the head position of the track of the cache memory, so that the position to the subsequent record is determined. There was a problem that it took time.

[Means to solve the problem and its action]

In order to solve the above problem, the present invention stores the address of the previous cache memory and the designated sector value obtained by the set sector command at a specific position of the track of the cache memory, and then sets the next set sector command. Is given, the sector value stored in the specified position is compared with the specified sector value in the command, and if the specified sector value is larger than the stored sector value, the address position stored in the specified position is read. By tracing the record to find the address corresponding to the designated sector, the time is shortened as compared with the conventional method of always tracing the record from the head position of the track.

The basic configuration of the present invention is shown in FIG. In addition, Fig. 2 (a),
(b) shows the recording arrangement of tracks on the magnetic disk and the corresponding storage arrangement on the cache memory according to the present invention.

In FIG. 1, a solid line frame indicates a disk cache controller, 1 is a cache memory, 2 is a data register, 3 is an address register, 4 is a plurality of registers 41 to 46.
And the like, 5 is an X register, 6 is a Y register, 7 is an arithmetic circuit, 8 is a discrimination circuit, 9 is a control circuit, 1
Reference numeral 0 indicates a program memory, and 11 and 12 indicate buses.
And control gates between circuits.

The arrangement of the track data of FIG. 2 (a) stored in the cache memory 1 is shown in FIG. 2 (b).

Of the storage arrangement of the cache memory shown in FIG. 2 (b), the prefix portion is unique to the present invention. When the track is accessed, the prefix portion is used as an area for storing a designated sector value given by a command at the time of access and a cache memory address obtained by the sector value as a set.

The content of this prefix part is rewritten each time it is accessed, and the content is used to make the next access more efficient. The prefix part is provided at a specific position of the data position of each track, and is located before the home address part of the track in this example.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the operation flow of FIG. Note that FIGS. 1 and 2 (a) and (b) are referred to.

In step, when a set sector command (not shown) is given from the CPU side, the designated sector value is stored in the register 41 of the data memory 4. In this case, the designation of the track and the start address of the track in the cache memory are given together with the designated sector, but the address of the start position of the track in the cache memory will be described as 0.

The control operation started by receiving the set sector command, in the next step, is the prefix portion of the track of the cache memory 1 (see FIG. 2).
(b)) is read at an address according to the address register 3 (address before k word from address 0, where k is the number of prefix words). The contents of the prefix part are set as the sector value m and the memory address P in 42 and 43 of the cache memory 1 via the data register 2 and whether the contents are other than 0 (whether or not the value is set)
Is discriminated by the arithmetic circuit 7 and the discrimination circuit 8.

If the value is set, it is clear that the data of any record of this track has been previously accessed, and in the next step, the sector value (m) which was previously accessed is set. A record 41 that holds the contents of the register 42 that holds the specified sector value St
The contents of the above are discriminated by the arithmetic circuit 7 and the discrimination circuit 8.

If m = St here, it means that the specified sector value to be obtained matches the sector value at the time of the previous access, and the memory address to be obtained is 43 in the cache memory 1.
Since it is the memory address P of the prefix stored in, the process ends here.

If m <St is determined in the step, it is found that the designated sector value St of this time is rearward on the track, compared to the sector value (m) of the previous access,
In order to start the address calculation based on the sector value m at the time of the previous access and the memory address P at that time, the values of m and P are transferred from the cache memory 1 to the X register and the Y register, respectively, in step.

The step is to determine the ending condition of the program loop to be positioned, and it is checked whether or not the data representing the index is written in the memory location.

In this case, since the address P does not have an index, control is passed to the next step, and the operation of the following equation is executed here.

X + (Li + G) / Sn → X (1) Y + Li → Y (2) Formula (1) is the previous sector value m in the X register 5 and the corresponding record in the count part of the record in the area 46. Data length Li (including word length of count part) and recording gap (fixed word length) G, divided by 1 sector word length (fixed word length) Sn (record word length and gap) And the value obtained by converting the length into the number of sectors) are added and stored in the X register 5.

Further, the expression (2) is obtained by adding the data length of the record to the address P which is the content of the Y register 6 and storing the result in the Y register 6 so that the address of the record next to the record of the address P is obtained. Is what you get.

Recording gap length G and 1 used to calculate equations (1) and (2)
The sector word length Sn is the register 45, 4 in the data memory 4.
4 respectively.

When the calculation is completed, the process proceeds to the next step, the contents of the X register 5 storing the sector value of the next record obtained by the calculation are compared with the contents of the register 41 storing the designated sector value St, and X <St , It is found that the record corresponding to the designated sector value is at a position further after, so that the process returns to the step and the operation already described is performed from there.

If it is determined to be XSt in the step, the sector value of the X register 5 coincides with or exceeds the designated sector value St. Therefore, the memory address value stored in the Y register 6 at this time is the designated sector value St. Since it is the desired memory location corresponding to, the operation ends here.

Here, returning to the step, if there is no data in the prefix portion, that is, if the set sector command has not arrived for that track before that, move to step and the sector value In order to perform the calculation, the value 0 representing the sector 0 is set in the X register 5 and the start address 0 of the track on the cache memory is set in the Y register 6, and then the step proceeds to the above-mentioned operation. Are performed sequentially.

If m <St is determined in the step,
Since the sector value m at the time of the previous access is located after the specified sector value this time, the prefix value in the step is calculated in order to calculate the sector value in order from the first record of the track without using the data of the prefix part. The same process as when there is no data in the section is executed in steps.

In the step, when the contents of the Y register 6 are set in the address register 3 and read from the cache memory, if the contents are not record data but the index is detected, the process proceeds to step. In this case, the index (HA) which is the head position of the track is detected in the process of tracing the records one by one, which means that the previous record has the word length up to the last sector position and the track Since the record position next to is the first position on the track of the magnetic disk as shown in FIG. 2 (a), the memory address to be obtained is the top memory address of the track, so 0 is set in the Y register 6. Set and finish.

In this way, the address on the cache memory corresponding to the designated sector given by the set sector command is obtained in the Y register 6 and the positioning is completed.

After the positioning is performed, it is necessary to write the specified sector value and the obtained memory address by the command of this time in the prefix part of the cache memory.

〔The invention's effect〕

According to the cache memory positioning method of the present invention, compared with the conventional method of always sequentially tracing the record from the head position of the track, when the sector value is the same as or larger than the sector value at the time of the previous positioning, particularly in the case of positioning to the record after the position It is possible to reduce the number of operations until positioning to the specified sector,
Positioning time can be shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention, and FIG. 2 (a) is a diagram showing a recording format on a track of a magnetic disk,
FIG. 2 (b) is a diagram showing a memory arrangement of a cache memory according to the present invention, FIG. 3 is a diagram showing an operation flow of the embodiment of the present invention, and FIG. 4 (a) is a recording on a track of a conventional magnetic disk. FIG. 4 (b) is a diagram showing a format, and FIG. 4 (b) is a diagram showing a storage arrangement of a cache memory of track data by a conventional method corresponding to FIG. 4 (a). In FIG. 1, 1: cache memory 2: data register 3: address register 4: data memory 5, 6: X, Y register 7: arithmetic circuit 8: discrimination circuit 9: control circuit 10: program memory

Claims (1)

[Claims] 1. In a disk cache of a magnetic disk of a variable length recording format, a sector value of a track of the magnetic disk and an address on the cache memory corresponding to the track are recorded at a specific position corresponding to each track on the cache memory. An area for storing information as a set is provided, and the set information at a specific position corresponding to each track is an address on the cache memory obtained for each access to a specified track on the cache memory specifying a sector value. The sector value of the set information stored in the specific position of the corresponding track is read out by accessing the specified track of the cache memory which is rewritten by the specified sector value and the sector value is specified. Means are provided for comparing designated sector values to ensure that the designated sector value is the same as the stored sector value or not. If it is larger, the address stored in the above group is used as the starting point of the address calculation corresponding to the specified sector value, and if the specified sector value is smaller than the stored sector value, the head record address of each track corresponds to the specified sector value. A cache memory positioning method characterized by locating the address on the cache memory corresponding to the specified sector value by sequentially obtaining the sector value from each record as the starting point of address calculation.