JP3221330B2 - Buffer control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buffer control method, and more particularly to a buffer control method for controlling a timing at which data stored in a buffer is transferred from a host device to a recording device.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show a conventional example. In FIG. 5, the host device 51 sends out data to be recorded on the recording device 53. The buffer 52 temporarily stores and holds the data sent from the host device 51. Recording device 5
3 records data transmitted from the buffer 52 at a predetermined timing on a predetermined recording medium. The recording device 53 is, for example, a magnetic disk device or a magnetic tape device. The control device 54 periodically checks the amount of data stored in the buffer 52 and, when the amount of storage exceeds a preset threshold, causes the recording device 53 to send the stored data. When the amount of data stored in the buffer 52 is not increased for a certain period of time, the control device 54 sends the stored data at that time to the recording device 53 even if the amount of storage does not reach the threshold. I have.

FIG. 6 is a flowchart of the buffer control performed by the control device 54. The control device 54 periodically executes the following one operation. First, examine the accumulated amount P of the data in the buffer 52 (step S101), the accumulated amount P is determined whether it is greater than a predetermined threshold P ₀ (step S102). As a result, if exceeding the threshold value P _0, then it sends the data that is currently stored in the buffer 52 to the recording device 53, subjecting the data to the write processing in the recording device 53 (step S105). This completes one process.

On the other hand, in step S102, if the data accumulation amount P in the buffer 52 has not yet exceeded the threshold value P ₀ , the elapsed time T from the time when the host device 51 has written the latest data into the buffer 52 has been reached. to check (step S103), and determines whether the elapsed time T exceeds the predetermined time T ₀ which is set in advance (step S104). As a result, if the elapsed time T does not exceed the fixed time T ₀ , data transfer from the buffer 52 to the recording device 53 is not performed, and one process ends.

On the other hand, in step S104, when the elapsed time T has not been performed new write beyond a predetermined time T _0, then sends the data that is currently stored in the buffer 52 to the recording apparatus 3, data This is used for the writing process in the recording device 53 (step S105). This completes one process.

Conventionally, the recording device 5
3, the efficiency of data writing has been improved.

[0007]

However, in the above-mentioned conventional example, the buffer 52 is generally transmitted from the host device 51.
Since the speed at which data is written to the storage device 53 is faster than the speed at which data is written from the buffer 52 to the recording device 53, the threshold value of the buffer accumulation amount for sending data from the buffer 52 to the recording device 53 is set to a relatively large value. When data is written from the host device 51 to the buffer 52 at high speed and in large amounts, the data stored in the buffer 52 that has been accumulated up to that point cannot be processed, and the data writing process from the host device 51 to the buffer 52 waits. Was inconvenient.

Therefore, if the threshold value of the buffer accumulation amount for transmitting data from the buffer 52 to the recording device 53 is set to a small value, the frequency of data transmission from the buffer 52 to the recording device 53 increases, and the buffer 52 is likely to be empty. In the recording device 53, the recording state and the recording standby state are frequently repeated.
Is a magnetic disk drive, the positioning operation of the magnetic head is frequently performed. As a result, the positioning operation requires time, and after all, it is not possible to perform quick data ejection from the buffer 52 to the recording device 53. May be
Therefore, there is an inconvenience that the data write process from the host device 51 to the buffer 52 may be delayed.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to improve the disadvantages of the prior art and, in particular, when a large amount of data is sent from a high-order device at high speed, without waiting for a process of writing data to a buffer from the high-order device. It is an object of the present invention to provide a buffer control method capable of efficiently writing data to a recording device.

[0010]

Means for Solving the Problems To achieve the above object,
Therefore, according to the present invention , in a buffer control method for controlling the timing at which data stored in a buffer is sent from a higher-level device to a recording device, the data storage amount P _n-1 (n = 1,2 , 3,...), And checks the data accumulation amount P _n of the buffer after a predetermined time t set from the time point.
from _n-1 test was the amount of accumulated data P _n and calculates the differential _{D n = (P n -P n} -1) / t of the accumulation amount, the data storage amount in the up data accumulated amount P _n examined integral I _n = calculates _{(P 1 + P 2 + ...} + P n-1 + P n) · t, the differential D _n and the integral I _n checks the data storage amount P _n and the respective values multiplied by the predetermined weight The sum is calculated, and when the sum exceeds a predetermined value, the data stored in the buffer is sent to the recording device.

According to the present invention, the amount of data written per unit time from the host device to the buffer increases, the amount of data stored in the buffer increases, or the amount of data stored in the buffer elapses for a long time without much change. Then
Data is transferred from the buffer to the recording device.

[0012] With these, the above-mentioned object is to be achieved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
A description will be given based on FIGS. Here, since the physical configuration of the present embodiment is the same as that of the conventional example, description will be made with reference to the block diagram of FIG. This embodiment differs from the conventional example in that
This is a control method of the buffer 52 performed by the control device 54.

That is, in the buffer control method for controlling the timing of sending the data stored in the buffer 52 from the host device 51 to the recording device 53, the control device 5
4 is the data accumulation amount P of the buffer 52 at a certain point in time.
_n-1 (n = 1, 2, 3,...) are stored, the data storage amount P _n of the buffer 52 is checked after a predetermined period of time t from the time point, and the stored data storage amount P _{n− From 1} and the inspected data accumulation amount P _n , the derivative of the accumulation amount D _n = (P _n
−P _n−1 ) / t, and the integral I _n = (P ₁ +) of the data accumulation amount up to the inspected data accumulation amount P _n.
P ₂ + ... + calculates _{P n-1 + P n)} · t, and calculates the sum C _n of each value obtained by multiplying a predetermined weight to a differentiator D _n and integral I _n the amount of accumulated data was examined with P _n, when the sum C _n exceeds a pre-set constant value, so as to deliver the data stored in the buffer to the recording device. Here, the equation for calculating the sum C is shown in equation (1).

[0015] _{C n = K 1 · P n} + K 2 · I n + K 3 · D n ··· Equation (1)

In the above equation (1), K ₁ , K ₂ , K
₃ indicates a predetermined weighting factor. Also, n is a natural number, and as a result of the inspection of the data accumulation amount of the buffer 52 by the control device 54, the data accumulation amount of the buffer 52 becomes 0
It is assumed that n = 1 when n disappears, and thereafter, n is incremented by one each time the control device 54 checks the data accumulation amount of the buffer 52. When the amount of data stored in the buffer 52 becomes 0 again, it is assumed that the processing starts from n = 1 again.

Next, the control operation of the buffer 52 by the control device 54 will be described with reference to FIG. The control device 54
The following operation is repeatedly executed every time a certain sampling period t elapses.

That is, when the sampling period t elapses (step S1), the data accumulation amount P _n of the buffer 52 at the present time is checked, and this value is stored in the memory (step S2). Here, it is assumed that the data storage amount P _n-1 inspected last time is stored in the memory in advance.

Subsequently, the control device 54 calculates the product P _n · t of the data accumulation amount P _n of the buffer 52 acquired in the current inspection and the sampling period t by the integral I _n−1 of the data accumulation amount up to the previous time. _{= (P 1 + P 2 +} ... + P n-2 + P n-1) is added to · t, and calculates the integral I _n the amount of data accumulated up to this time (step S3). Here, the integral I _n-1 up to the previous time is
It is assumed that the integral In has been stored in the memory in advance, and the integral I _n calculated this time is updated in the memory in place of the integral I _n−1 calculated previously. Also, the data accumulation amount _Pn acquired this time is 0
, The integral I _n = 0 is stored in the memory and initialized.

[0020] Subsequently, the controller 54 calculates a differential D _n data storage amount based on the obtained data accumulated amount P _n preceding time and current time of the data storage amount P _n-1 (step S
4). Here, either of the processes of steps S3 and S4 may be performed first.

Then, the control device 54 calculates the above equation (1)
By calculating the sum C (step S5), and if it exceeds the threshold value C ₀ of the sum C is set in advance (step S6), and
The data currently stored in the buffer 52 is stored in the recording device 5.
3 is sent to (step S7), and does not exceed the threshold value C _0, without sending the stored data, the process ends.

According to this, the amount of data written per unit time from the host device 51 to the buffer 52 increases, the amount of data stored in the buffer 52 increases, or the amount of data stored in the buffer 52 does not change much. If a long time passes, the data is transferred from the buffer to the recording device, so not only when the buffer is full or when the data in the buffer that has been accumulated to some extent has not been sent out for a long time, When high-speed and large-volume data is transmitted from the higher-level device, data transmission to the recording device is started immediately, so that there is more free space for storing data transmitted from the higher-level device than in the conventional example. The buffer can be secured, and the data transfer speed can be increased without relatively waiting for data write processing from the host device to the buffer. It is possible to perform efficient data write with above.

[0023]

Next, the above embodiment will be described using specific numerical values with reference to FIGS. In the present embodiment, the host device 51 is a host computer, a recording device 52
Is a magnetic tape device. Further, the buffer 52 and the control device 54 may be provided in the housing of the host computer 51 or the magnetic tape device 53, or may be provided as independent housings.

Here, the maximum data transfer rate from the host computer 51 to the buffer 52 is 5 Mbytes / sec. The maximum data transfer rate from the buffer 52 to the magnetic tape device 53 is also assumed to be 5 Mbytes / sec. The sampling period of the control device 54 is t = 10 μsec. The maximum storage capacity of the buffer 52 is 500 kbytes. The tape repositioning time in the magnetic tape device 53 is set to 150 msec.

FIG. 2 shows a data transfer pattern from the host computer 51 to the buffer 52. As shown in FIG. 2, the data transfer from the host computer 51 to the buffer 52 takes the first 250 milliseconds at a data transfer rate of 1
Data transfer is interrupted for 50 ms, and the next 150 ms is transferred at a data transfer rate of 5 Mbytes / sec.
Seconds, then suspend data transfer for 100ms,
Is repeated.

Further, the weighting coefficient K in the above equation (1)
The values of ₁ , K ₂ , and K ₃ are K ₁ = for the proportional element.
0, K ₂ = 1 / 10,000 for the integral element, K ₃ = 0.6 for the differential element, and the threshold C ₀ = 10.

If the time when the data transfer from the host computer 51 to the buffer 52 is started is set as the start time of the sampling cycle, first, when t = 10 μs elapses (step S1 in FIG. 1), the control device 54 52
Get the data accumulation amount P ₁ (step S2). The data accumulation amount (proportional element) at this time is P ₁ = 0.01 k
Bytes (10 bytes).

Next, the integral element I ₁ when t = 10 μs has elapsed is the product of the proportional element P ₁ = 10 bytes and the sampling time t = 10 μs, and the integral element I ₀ = 0 at the time of the previous sampling. (Initial value).
₁ = is _{I 0 + P 1 · t =} 0.1m byte second (100 bytes · μ seconds) (step S3).

On the other hand, the differential element D is the difference between the proportional element P ₀ = 0 byte (initial value) at the time of the previous sampling and the proportional element P ₁ = 10 bytes at the time of the current sampling, and the sampling time t = 10 μm. It is obtained as a quotient divided by seconds, and D ₁ = 1 M / sec (1 byte / μsec) (step S4).

From the above equation (1), the buffer state C
Is: C = 1/50 × 0.01 + 100,000 × 0.1 + 0.6
From × 1, it becomes about 0.6 (step S5).

As a result, the buffer state C becomes the threshold value C ₀ =
Since it is smaller than 10 (step S6), no data is sent from the buffer 52 to the magnetic tape device 53.

Next, 20 μm from the start of the sampling period
When seconds have elapsed (step S1), the controller 54 obtains the data accumulation amount P ₂ of the buffer 52 in the same manner as described above (step S2). The data storage amount at this time is P ₂ =
0.02 kbytes (20 bytes).

When the integral element I is obtained in the same manner as the previous time, the proportional element P ₂ = 20 bytes and the sampling period t =
10 microseconds, from the previous integral element I ₁ = 100, I ₂ =
This is 0.3 mbytes / sec (300 bytes / μsec) (step S3).

Similarly, as for the differential element D, the proportional element P ₂ = 20 bytes, the sampling time t = 10 μs, and the previous proportional element P ₁ = 10 bytes, D ₂ = 1 Mbyte / sec (1 byte / μsec) (step S4).

The buffer state C at this time is calculated to be about 0.6 (step S5), and the write condition is not satisfied (step S6).

Thereafter, the above operation is repeated, and when 316.761 msec has elapsed from the start of data transfer, the buffer state C exceeds the threshold value C _0, and the condition for writing data from the buffer 52 to the magnetic tape device 53 is satisfied ( Step S6). Therefore, the control device 54 transfers the stored data from the buffer 52 to the magnetic tape device 53 and starts writing (step S7).

FIG. 3 shows the buffer 52 in the above embodiment.
FIG. 11 is a diagram showing a change in the amount of data stored in the storage device during a period of 250 ms from when data is transmitted from the host computer 51 at a speed of 1 Mbyte / sec to when the transmission is interrupted. It increases, and 250 Kbytes are accumulated when 250 msec has elapsed. After that, during 50 msec, the data transmission from the host computer 51 is suspended, so that the accumulated amount does not change. Then, after 300 msec has elapsed, the host computer again returns 5M
Data is transmitted at a rate of bytes / second, and the accumulated amount of the buffer 52 further increases. After that, 316.761m
When the second has elapsed, the value of C exceeds the threshold value C ₀ as described above, and data transmission from the buffer 52 to the magnetic tape device 53 is started. At this time, since the data transfer speed from the host computer 51 to the buffer 52 is equal to the data transfer speed from the buffer 52 to the magnetic tape device 53, the amount of data stored in the buffer 52 is kept constant. Thereafter, when the data transmission from the host computer 51 is interrupted, the accumulated amount of the buffer 52 linearly decreases and becomes empty.

On the other hand, FIG. 4 is a comparative example showing a change in the data storage amount when data transmission from the host computer shown in FIG. 2 is processed by the conventional buffer control. Here, the threshold value of the data storage amount (α in FIG. 6) is 25
It is assumed that it is 0K bytes. According to this, the data storage amount increases up to 250 ms after the data is sent from the host computer 51, as in the above-described embodiment.
When 50 milliseconds have elapsed, the host computer 51
Data transmission from the magnetic tape unit 53 is interrupted.
, The buffer is emptied when 300 ms has elapsed.

Then, the magnetic tape device 53 stops receiving the data to be written on the tape, and thus stops the tape feeding. However, in general, the sudden stop does not work, and the tape is sent or returned across the target stop point. Or repositioning to the target position while repeating (repositioning). However, since the data transmission from the host computer 51 is resumed with the elapse of 300 ms, the data storage amount of the buffer increases again during this time. Here, if the repositioning operation requires 150 ms, the magnetic tape device cannot receive data during repositioning. Therefore, even if the data storage amount of the buffer exceeds 250 Kbytes, The buffer capacity eventually becomes full.

When the buffer capacity becomes full, the data transmitted from the host computer 51 is not accepted by the buffer, and the transmission of data is awaited. And 45
When the data can be received by the magnetic tape device after the elapse of 0 ms, the data transmission from the buffer is restarted, and the host computer 51 also restarts the data transmission according to the secured free space of the buffer. Then 5
00 msec has elapsed and the host computer 51
If the transmission of data to be completed by 50 ms is completed with a delay, the amount of data stored in the buffer decreases.

Thus, in the embodiment and the comparative example,
A substantial difference occurs in the data transfer speed. According to the above embodiment, the data transfer speed can be improved as compared with the conventional example.

Here, in the above-described embodiments and examples, the data transmission timing from the buffer to the recording device is controlled based on the proportional element, the integral element, and the differential element. The data transmission timing may be controlled based on a combination of the proportional element and the differential element.

That is, in the buffer control method for controlling the timing of sending the data stored in the buffer from the host device to the recording device, the data storage amount P _n-1 (n = 1, 2, 3,...), And checks the data accumulation amount _Pn of the buffer after a predetermined time t set from the time point.
A differential D _n = (P _n −P _n−1 ) / t of the storage amount is calculated from _n−1 and the inspected data storage amount P _n, and this differential D _n is calculated.
Is calculated by multiplying the data accumulation amount _Pn and the inspected data accumulation amount by a predetermined weight, and when the sum exceeds a predetermined value, the data accumulated in the buffer is sent to the recording device. It may be configured to transmit.

Further, in the buffer control method for controlling the timing at which the data stored in the buffer is sent from the higher-level device to the recording device, the data storage amount P _n-1 (n = 1, 2, 3,...), And checks the data accumulation amount _Pn of the buffer after a predetermined time t set from the time point.
from _n-1 test was the amount of accumulated data P _n and calculates the differential _{D n = (P n -P n} -1) / t of the accumulation amount, the data storage amount in the up data accumulated amount P _n examined integral I _n = calculates _{(P 1 + P 2 + ...} + P n-1 + P n) · t, the differential D _n and the integral I _n checks the data storage amount P _n and the respective values multiplied by the predetermined weight The sum may be calculated, and when the sum exceeds a predetermined value, the data stored in the buffer may be transmitted to the recording device.

[0045]

Since the present invention is constructed and functions as described above, according to the present invention, the amount of data stored in the buffer is made a proportional element, its differential element is calculated, and the recording device is converted from the buffer based on the differential element. Control the timing of sending data to the storage device, so that a high-speed and large amount of data is sent from the host device, and when the amount of data per unit time written to the buffer from the host device increases, the data sending to the recording device starts immediately, An empty area for storing data sent from the host device can be secured in the buffer more quickly than in the conventional example, and the data transfer speed is improved without having to wait for data writing from the host device to the buffer. Thus, efficient data writing can be performed.

[0046] Further, since the control data transmission timing based on both the differential element and the proportional element, if the data transfer from the host device to the buffer is slow, the data transfer is suppressed from the buffer to the recording device Although the capacity of the buffer can be effectively used, a large amount of data can be transferred to the recording device at one time, and the data processing efficiency of the recording device can be improved. on the other hand,
When data transfer from the higher-level device to the buffer is fast, by transmitting data from the buffer to the recording device as described above, a necessary data storage area in the buffer can be secured.

In addition, since the data transmission timing is controlled based on each of the differential element, the proportional element, and the integral element, information on how much and how much data in the buffer is left by the integral element can be obtained. Compared to the conventional buffer data transmission control on the condition that a predetermined time elapses, transmission timing control can be performed in consideration of the amount of data stored in the buffer, and in addition to the above effects, more optimal buffer control can be realized. It is possible to provide an excellent buffer control method that has never been achieved before.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation of one embodiment of the present invention.

FIG. 2 is a diagram showing a pattern of data transmitted from a higher-level device to a buffer in an embodiment of the present invention.

FIG. 3 is a diagram illustrating a change in a data accumulation amount of a buffer according to the embodiment of the present invention.

FIG. 4 is a diagram showing a change in a data accumulation amount of a buffer in a comparative example with the embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional example.

FIG. 6 is a flowchart showing the operation of the conventional example.

[Explanation of symbols]

 Reference Signs List 51 Upper device (host computer) 52 Buffer 53 Recording device (magnetic tape device) 54 Control device

Claims (1)

(57) [Claims] 1. A buffer control method for controlling a timing at which data stored in a buffer is sent from a higher-level device to a recording device, the method comprising:
_{n-1 (n = 1,2,3,} ...) stores, examines the stored data amount P _n of the buffer in the previously set predetermined time t after the time point, the stored data accumulated amount P _n The differential D _n = (P _n −P _{n -1} ) of the accumulated amount from ₋₁ and the inspected data accumulated amount P _n.
/ T to calculate the, integration of data accumulation amount in until the data accumulation amount P _n that the inspection _{I n = (P 1 + P} 2 + ... + P n-1 + P n) · t
Is calculated, the calculated sum of the differential D _n and the integral I _n as defined above test was in the amount of accumulated data P _n value obtained by multiplying a predetermined weight, the sum exceeds a preset fixed value A buffer control method for transmitting the data stored in the buffer to the recording device.