JP3043631B2 - File look-ahead system and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a high-speed file read-ahead system and method for reading data in a file device.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a configuration of a conventional processing method for reading data from a file device.

This system employs an input / output parameter holding means 1
, A logical volume 2 and an output data holding unit 3 constitute a file device. A read command is input to the input / output parameter holding unit 1, and the file device sets the concatenated data from the logical volume 2 as one block. Is transferred to the output data holding means 3 and the data stored in the output data holding means 3 is output through the input / output parameter holding means 1, so that the data stored in the file device can be read. It is.

[0004] As a conventional method for improving the performance of data transfer speed, there is a "disk cache efficiency method" described in Japanese Patent Application Laid-Open No. 01-082239, which is a logical volume specified by an actual read command. At a time, reads several blocks of continuous data from the physical position at a time, stores the read data in the cache buffer, reduces the number of times of reading from the logical volume, and retrieves data at the same physical position as the previously read data When a read command is received, the data transfer speed is improved by extracting data from the cache buffer.

Japanese Patent Laid-Open No. 03-102 discloses a method for improving read-ahead performance and efficiently using a memory.
There is a "data prefetch control method" described in Japanese Patent No. 443, and when prefetching, by determining a sequential access read and a random access read based on a predetermined number of access histories, the prefetch performance of the sequential access read is improved. It allows for improved and efficient use of cache memory.

[0006]

Problems to be Solved by the Invention
In the "Disk Cache Efficiency Method" described in Japanese Patent Application Laid-Open No. 082239, the time from when a series of read processing is completed in the file device to when the next command is received is wasted time when there is no access to the logical volume. Had been raised.

In the "data pre-reading control method" described in Japanese Patent Application Laid-Open No. 03-102443, switching from random access reading to sequential access reading is followed by switching to random access reading during a predetermined number of accesses. In such a case, there is a case where the prefetching process is not performed at all even though the sequential access read is performed.

Therefore, an object of the present invention is to improve the data reading speed in a file device in order to solve the above-mentioned problems in the conventional system.

[0009]

According to the present invention, there is provided an input / output parameter for holding parameter data having a read command to be input, physical position information of a logical volume currently being executed or having been executed, and an execution result of a file device. Holding means and a logic capable of extracting data held from a specified physical position in accordance with a read command stored in the input / output parameter holding means, and interrupting processing during data extraction. In a readable file read-ahead system comprising a volume and output data holding means for holding data taken out from a logical volume together with physical position information, a physical memory for holding a history of read commands stored in an input / output parameter holding means Position history storage means and physical position stored in physical position history storage means Physical position estimating means for estimating the next physical position to be read based on the information, and when the read command is stored in the input / output parameter holding means, the physical position of the instruction register of the read command and the data stored in the output data holding means are stored. Physical position comparing means for comparing the read data with the physical position of the read data.
Position and the data stored in the output data holding means.
If the physical location does not match,
Resetting interrupts prefetched access
Read processing to access the normal logical volume
To read the data, and if they match,
Do not access the logical volume and save the retained data
Output to improve the data read speed.
This is file prefetching system data characterized by the following.

Further, the physical position history storage means has a function of storing the physical location information of the past two as the history, the number of the stored physical location information to output the one of the signals not walk 2, 2 If less, complete the process and
In this case, the physical position prediction means
Enter the remembered physical location information, then read the physical
Preferably , the position is predicted and the predicted physical position is stored .

Further, the physical position estimating means is set to
From the physical position of the logical volume executed immediately before, the direction toward the physical position of the immediately preceding instruction is determined as the read direction, and the physical position of the next block in the read direction is the next physical position to be read. Is preferably determined.

It is preferable that the physical position comparing means has a function of storing a result of the comparison.

The file read-ahead method of the present invention further comprises a read command to be input and parameter data including physical position information of a logical volume currently or after being executed;
An input / output parameter holding procedure that holds the execution result of the file device and a read command stored by the input / output parameter holding procedure are used to retrieve the retained data from the specified physical location, and interrupt processing while retrieving the data. In a readable file pre-reading method, which includes a logical procedure to execute and an output data holding procedure for holding data extracted by the logical procedure together with physical position information, a history of read commands stored by an input / output parameter holding procedure is held. A physical position history storage procedure, and a physical position prediction procedure for predicting a next physical position to be read based on the physical position information stored in the physical position history storage procedure,
When the read command is stored by the input / output parameter holding procedure, the method further includes a physical position comparing procedure of comparing the physical position of the instruction register of the read command with the physical position of the data stored by the output data holding procedure, The physical position prediction procedure takes the two immediately preceding physical position information.
And the logical volume executed immediately before
From the physical location of the volume, the physics of the immediately preceding instruction
Determining the direction toward the position as the readout direction
And the physical position of the next block in the read direction
Determining the next physical position to be read .

In particular, the file read-ahead system of the present invention accumulates, as history information, read commands executed by the file device in the past, and accumulates the read commands immediately after the operation of the file device according to the actually received command is completed. The physical position of the logical volume to be read next is predicted from the history information, one block of data is read from the predicted physical position of the logical volume, and the data is held inside the file device. Is received, if the physical position of the read command does not match the predicted physical position, access to the normal logical volume is performed after interrupting the prefetching access that was performed by resetting the logical volume. Switch to read processing, perform read processing, and the predicted physical location of the logical volume matches If you do not access the logical volumes, by outputting the data held in the file system, thereby improving the speed of reading data.

In this way, the read command executed by the file device in the past is accumulated from the input / output parameter holding means as history information in the physical position history storage means, and the file device according to the actually received read command is stored. Immediately after the operation is completed, the physical position of the logical volume to be read next is predicted from the physical position history information accumulated in the physical position history storage means, the predicted physical position of the logical volume is converted into a read command, and the input / output parameter holding means is read. And the logical volume transfers one block to the output data holding means according to the instruction stored in the input / output parameter holding means. When the actual read command is received by the input / output parameter holding unit, the physical position of the read command stored in the input / output parameter holding unit is compared with the physical position of the data of the output data holding unit by the physical position comparing unit, and the data is compared. Otherwise, resetting the logical volume during the read operation interrupts the prefetching access which has been excessive, and then proceeds to the process of reading data from the logical volume in accordance with the read command stored in the input / output parameter holding means. Switch to perform read processing, transfer data from the logical volume to the output data holding means, output read data through the input / output parameter holding means, and predict the physical position of the read command stored in the input / output parameter holding means as the predicted logical volume. If the physical locations of the logical volumes match, Seth is not performed, by outputting the data of the output data holding means through the input-output parameter storage, it is possible to improve the speed of reading the data in the file system.

[0016]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the file prefetch system of the present invention.

This system comprises an input / output parameter holding unit 1, a logical volume 2, and an output data holding unit 3.
Physical position history storage means 4 and physical position prediction means 5
And physical position comparing means 6.

Each means will be described. Here, the physical position information indicates a cylinder number, a track number, and a sector number.

The input / output parameter holding means 1 is an interface between the file device and the outside. The input / output parameter holding means 1 has an instruction code for instructing a read operation, physical position information indicating the physical position of the logical volume 2, and transfer from the output data holding means 3. And a function of retaining output data to be output. The configuration is such that a register for storing an instruction code for instructing a read operation of the file device, physical position information of the logical volume 2 from which data is to be read, and data of the output data holding means 3 which are temporarily output to the outside of the file device. (1 in FIG. 1).

The logical volume 2 holds the data, and transfers the data at the specified physical position to the output data holding means 3 by inputting a read command and physical position information accompanying the command. When a reset signal is received while the logical volume 2 is operating, the logical volume 2 has a function of stopping the operation and operating the logical volume 2 so that the next read command can be received. The logical volume 2 is a magnetic disk for storing data (2 in FIG. 1).

The output data holding means 3 is a logical volume 2
Has a function of temporarily holding data transferred from the server and its physical position information, and notifying a holding status as to whether or not the data is currently held. That is, it is a random access memory having a function of temporarily storing data to be read from the logical volume 2 and its physical location information, and has a flag register indicating whether data is stored. In the initial state where no data is stored, 0 is stored, and after data is stored, 1 is continuously stored (3 in FIG. 1).

The physical position history storage means 4 is a storage device for storing the physical position information stored in the input / output parameter holding means 1, stores the physical position information of past several times as a history, and stores the stored physical position information. It has a function of outputting a signal indicating whether or not the number is two or more. That is, the physical position history storage unit 4 is a random access memory having a FIFO structure for storing the physical position information stored in the input / output parameter holding unit 1. (4 in FIG. 1).

The physical position predicting means 5 has a function of predicting a physical position to be read next based on a history of past physical position information held in the physical position history storing means 4, and a function of holding the predicted physical position. Having. That is, the physical position predicting means 5 has a random access memory for storing the predicted physical position (5 in FIG. 1).

The physical position comparing means 6 stores the physical position information held by the input / output parameter holding means 1 or the physical position held by the physical position estimating means 5 and the physical position held by the output data holding means 3. Compare with location information,
If not the same, it has the ability to output a reset signal to the logical volume 2. As a prediction method of the physical position to be read next, among the physical positions stored in the physical position history storage unit 4, the instruction executed immediately before from the physical position of the logical volume 2 of the instruction executed immediately before the immediately preceding instruction is executed. The direction toward the physical position of the instruction is determined as the read direction, and the physical position of the next block in the read direction of the physical position read immediately before is determined as the physical position to be read next. That is, the physical position comparing unit 6 stores the physical position information stored in the crowding storage unit 1 or the physical position information stored in the physical position estimating unit 5 and the output data storing unit 3. This is a comparison circuit having a function of comparing with existing physical position information. It also has a function of storing the result of comparison (6 in FIG. 1).

FIG. 3 is a flowchart showing a read operation of the file prefetch system of the present invention. Hereinafter, each step will be described.

First, when a read command and the physical position of the logical volume 2 from which data is to be read are input from the outside to the input / output parameter holding means 1, the physical position history storage means 4
The physical position history storage means 4 stores the input physical position information (steps 3-1 and 3).
-2).

Next, an inquiry is made as to whether the data is stored or not in the output data holding means 3 (step 3-3). At this time, the data storage status is acquired by referring to the flag register of the output data holding unit 3.

When data is stored in the output data holding means 3, the physical position comparing means 6 outputs the output data holding means 3.
Is compared with the physical position information of the data held in the logical volume 2 stored in the input / output parameter holding unit 1 (step 3-).
4).

If the physical positions are different, a reset signal is output to the logical volume 2 to reset the logical volume 2 (step 3-5).

If no data is stored in the output data holding means 3, the comparison operation and the reset operation are not performed (step 3-6).

The physical position information and the read command held in the input / output parameter holding means 1 are input to the logical volume 2, and the logical volume 2 outputs the data of the input physical position information to the output data holding means 3 I do. The output data holding means 3 stores the data (step 3
-7, 3-8).

Finally, by sequentially outputting data from the output data holding means 3 to the input / output parameter holding means 1, the read operation of this device is completed (step 3-10).

If the physical position comparison results in step 3-4 are the same, the data held in the output data holding means 3 is sequentially output to the input / output parameter holding means 1 to read out the data. The operation is completed (steps 3-9, 3-10).

Next, FIG. 4 is a flow chart showing an operation of predicting a physical position to be read next and prefetching data from a logical volume, which is a feature of the present invention.

First, this operation is started when the above-mentioned read operation is completed (step 4-1).

First, data is stored in the physical position history storage means 4.
That is, an inquiry is made as to whether there are two or more pieces of physical position information (step 4-2).

Next, when there are less than two data in the physical position history storage means 4, the processing is completed (step 4-
7).

When there are two or more pieces of data stored in the physical position history storage means 4, the physical position prediction means 5 inputs the physical position information stored in the physical position history storage means 4,
The next physical position to be read is predicted, and the predicted physical position is stored. As a method of predicting the next physical position to be read, the direction from the physical position of the logical volume 2 of the instruction executed immediately before the immediately preceding instruction to the physical position of the immediately executed instruction is determined as the read direction. The physical position of the next block is determined as the physical position to be read next in the reading direction of the physical position read at step (4-3).

The physical position comparing means 6 compares the predicted physical position held by the physical position history storing means 4 with the physical position of the data held by the output data holding means 3 (step 4-). 4).

Here, the existence of data in the output data holding means 3 is obvious because there are two or more pieces of physical position information data in the physical position history storage means 4.

As a result of the comparison, if the physical positions are the same,
Here, the process is completed (step 4-7).

As a result of the comparison, if the physical positions are different, the predicted physical position information and the read command are input to the logical volume 2 and the logical volume 2 outputs the data of the specified physical position to the output data holding means. 3 to complete the pre-read operation that predicts the physical position to be read next to this device (step 4-5).
Step 4-6).

The configuration and operation of the file read-ahead system of the present invention have been described above. Here, the file read-ahead system of the present invention is compared with the "disk cache efficient system" described in Japanese Patent Laid-Open No. 01-08239. The advantages of the look-ahead system of the invention will be described.

According to the "disk cache efficiency improvement method", when a read request for a certain block is issued, several blocks continuous from the block are read from the magnetic disk device and several blocks are stored in the disk cache buffer. Data is stored together. Next, when a read request is made, a cache hit determination is performed by the cache hit determination means, and if there is a hit, data is read from the disk cache buffer to reduce the number of times of reading from the magnetic disk device.
I / O efficiency is improved. Here, the magnetic disk device, the cache hit judging means, and the disk cache buffer correspond to the logical volume 2, the physical position comparing means 6, and the output data holding means 3, respectively, in the file read-ahead system of the present invention.

In comparison, the output time of data of one block length of the logical volume is constant, the data to be read is a sequential file, all blocks in which data exist are continuous, and the data to be read is sufficiently large. In addition, the processing speed performance of the devices corresponding to both inventions is assumed to be the same, and a condition for adding a constant time for receiving the next read command after the data read process is completed is added. This guarantees the most efficient data reading in both the "disk cache efficiency method" and the "file prefetch system" of the present invention,
This is to make the performance of the circuit used the same.

FIG. 5 shows the "disk cache efficiency improving method".
FIG. 5 is a diagram comparing read times of the “file prefetch system” of the present invention. (A) shows the data read time in the "disk cache efficiency improvement method", (B) shows the read time of the "file prefetch system", and (C) shows the symbols used in (A) and (B) Is explained.

The cache hit determination time is A, the time for reading one block of data from the magnetic disk and storing the data in the cache buffer is B, the time for outputting the data from the cache buffer is C, and the device has read the data from the completion of the read operation to the next. Let D be the time until the read command is received, E be the predicted time by the physical position predicting means 5 in the "file prefetch system" of the present invention, N be the total number of blocks to be read, and N be 1 or more. Here, the number of accesses to the magnetic disk device in the "disk cache efficiency method" is set to one, and the "disk cache efficiency method"
To maximize the data read efficiency.

From FIG. 5, the total access time SUM1 of the "disk cache efficiency improving method" is as follows.

SUM1 = N × (A + C) + (N−
1) × (B + D) + B + D Similarly, the total access time SUM2 of the “file prefetch system” of the present invention is as follows.

SUM2 = N × (A + C) + (N−
1) × max (D, (E + B)) + B + D (max (α, β): indicates an operator that compares the time of α and β and outputs the larger one) The time obtained by subtracting SUM2 from SUM1 is SUM SUM / (N-1) = (SUM1-SUM2) / (N-1) = (B + D) -max (D, (E + B)) In the case of D> (E + B), SUM / (N-1) = (B + D) -D = B (B
Is a numerical value exceeding 0).

This indicates that SUM always exceeds 0, and that the total access time of the “file read-ahead system” is always higher than that of the “disk cache efficiency method”. Indicates that it is short.
When D ≦ (E + B), SUM / (N−1) = (B + D) − (E + B) =
DE Here, the time D indicates the processing time of the CPU, and is a time of at least one clock. On the other hand, time E indicates the processing time of the physical position estimating means 5 and can be realized by a comparison circuit and an arithmetic circuit. In general, the same comparison circuit and arithmetic circuit exist inside the CPU. When the same circuit element is used, the following equation is established.

DE ≧ 0 (DE is a numerical value of 0 or more) This indicates that SUM is always a value of 0 or more, and the total access time of the “file prefetch system” is always “disk cache”. It is the same or shorter than the total access time of the “efficiency method”.

The above results show that the read time of the "file prefetch system" is shorter than that of the "disk cache efficiency method", and the speed performance is superior. The cause is that the reading process is started from the magnetic disk device during the time from when the file device completes the reading process to when the next reading command is received,
This is a feature of the present invention.

[0055]

According to the present invention, the physical position to be read next to the logical volume is predicted during the reception of the next command after a series of read operations is completed, the read processing is performed from the logical volume, and the next command is read. Is a read command and a sequential access read, it is possible to immediately output read data by prediction. Therefore, the data reading speed of the file device can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional file device.

FIG. 3 is a flowchart illustrating a read operation according to the embodiment of the present invention.

FIG. 4 is a flowchart illustrating a prefetch operation according to the embodiment of the present invention.

FIG. 5 is a diagram comparing the readout time between the conventional method and the system of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 I / O parameter holding means 2 Logical volume 3 Output data holding means 4 Physical position history storage means 5 Physical position prediction means 6 Physical position comparison means

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G06F 12/00

Claims (5)

(57) [Claims] 1. An input / output parameter holding means for holding parameter data having a read command to be input, physical position information of a logical volume currently being executed or having been executed, and an execution result of a file device, A logical volume capable of retrieving retained data from a specified physical position in accordance with the read command stored in the retaining means, and capable of suspending processing while retrieving the data; A read-out file read-ahead system comprising: output data holding means for holding data taken out from a volume together with the physical position information; and a physical position history for holding a history of read commands stored in the input / output parameter holding means. Storage means; physical data stored in the physical position history storage means Physical position estimating means for estimating a physical position to be read next based on the position information; and when a read instruction is stored in the input / output parameter holding means, a physical position of an instruction register of the read instruction; Physical position comparing means for comparing the physical position of data stored in the read instruction with the physical position of data stored in the read instruction.
The position and the data stored in the output data holding means.
If the physical location of the
Read-ahead access by resetting
After interrupting the normal logical volume read
Switch to readout processing, perform readout processing, and match
If not, keep the logical volume without accessing it
Output data to reduce the data read speed.
A file read-ahead system that has been improved . Wherein said physical position history storage unit stores the physical location information of the past two as the history, the number of the stored physical location information and outputting the one of the signals not walk two, 2 If less than two, complete the process and if more than two
The physical position predicting means stores the physical position history
Enter the physical position information stored in the stage, then read
2. The file read-ahead system according to claim 1 , wherein a predicted physical position is predicted, and the predicted physical position is stored . Wherein the physical position predicting means, from one physical location of the logical volume that was performed prior to immediately before, it determines the direction reads in a direction toward the physical location of the instruction to be executed the immediately before the read 3. The file read-ahead system according to claim 1, wherein a physical position of a next block in the direction is determined as a physical position to be read next. 4. The apparatus according to claim 1, wherein said physical position comparing means has a function of storing the result of the comparison.
4. The file look-ahead system according to any one of claims 1 to 3. 5. An input / output parameter holding procedure for holding a read command to be input, parameter data including physical position information of a logical volume being currently executed or executed, and an execution result of a file device. A logical procedure for retrieving retained data from a specified physical location in accordance with the read instruction stored according to a procedure, and interrupting processing during the retrieval of the data; A read-ahead file pre-reading method, comprising: a physical position history storing procedure for storing a history of read commands stored by the input / output parameter storing procedure; and a physical position history storing procedure. Based on the stored physical position information, the next physical position to be read is predicted. When a read instruction is stored by the input / output parameter holding procedure, a physical position of an instruction register of the read instruction is compared with a physical position of data stored by the output data holding procedure. A physical position comparing step of extracting the two immediately preceding physical position information from the physical position information.
And the physical location of the logical volume that was executed one immediately before
From the direction toward the physical location of the instruction executed immediately before
Determining the physical direction of the next block in the read direction.
Determining a physical position to be read next and a step of determining the physical position to be read next .