JPH04268655A - Input/output load distribution control system - Google Patents

Abstract

PURPOSE:To prevent a load from being partially applied to a specific peripheral control unit(PCU) in the computer system where plural input/output paths using different PCUs for peripheral device exist and one arbitrary input/output path is used to perform the input/output operation. CONSTITUTION:Load information of each PCU and information related to the PCU which uses each peripheral device just before are managed in a table. When plural PCUs which can control the peripheral device as the input/output object exist (existence of plural PCUs is discriminated in a step 22), load states of these CPUs managed on the table are compared with one another in steps 23 and 25, and an input/output path including the PCU of light load is selected in step 27 when they are different, but an input/output path including a PCU other than the PCU which uses the peripheral device managed on the table just before is selected (in steps 26 and 28) when they are not different.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an input/output load distribution control method for a computer system, and in particular, in a computer system equipped with a plurality of peripheral control devices that have a common peripheral device under their control, the present invention relates to an input/output load distribution control method for a computer system. This invention relates to an input/output load distribution control method that prevents load from being biased toward a specific peripheral control device.

0002

Conventionally, in this type of computer system, in a processing unit such as a central processing unit, each peripheral control device has its load status (for example, the number of input/output requests accepted by each peripheral control device) The number of unprocessed input/output requests (subtracting the number of input/output requests) is managed, and a certain peripheral device requested to perform input/output by an input/output request program is common to a certain plurality of peripheral control devices. If the peripheral device is a peripheral device, the processing device compares the load states of those peripheral control devices and processes the above-mentioned input/output request using the peripheral control device with a lower load. Additionally, if the loads are equal or there is no load on each other, the peripheral control device indicated by the first path preset for that peripheral device on the input/output path management table, etc. is used preferentially. .

0003

SUMMARY OF THE INVENTION Conventionally, load distribution of peripheral control devices has been attempted as described above, but the following problems have occurred.

That is, when input/output requests are issued continuously, load distribution is properly achieved, but when an input/output request to a certain peripheral device is issued from a single input/output request program, In many cases, the load status of multiple peripheral control devices under the peripheral device is the same or both are unloaded, so only the peripheral control device of the first path set in advance for the peripheral device is It's always used.

[0005] At this time, another loosely connected processing device also makes one input/output request to another peripheral device connected to the peripheral control device being used by the own processing device, in the same way as the own processing device. When a single input/output request is made from a program, if the peripheral control device indicated in the first pass of that other peripheral device is the same as the peripheral control device in use in its own processing device, other usable peripheral control devices will be available. Even though a peripheral control device exists, processing devices compete with each other for a specific peripheral control device, resulting in a decrease in input/output performance.

SUMMARY OF THE INVENTION An object of the present invention is to prevent the load from being concentrated on a specific peripheral control device even when an input/output request is issued sporadically.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the input/output load distribution control method of the present invention provides a plurality of peripheral control devices having a common peripheral device under their control, and a plurality of peripheral control devices having a common peripheral device under their control. In a computer system equipped with an input/output control device subordinate to it and connected to a processing unit, there is a table that holds load information of the peripheral control device and information of the peripheral control device most recently used for the peripheral device, and a table that holds information about the peripheral control device that was used most recently. input/output path selection means for selecting an input/output path by referring to load information and last used peripheral control device information held in the table at the time of an input/output request; The processing device includes input/output execution means for activating an input/output operation for the peripheral device via the processing device and updating the load information and the most recently used peripheral control device information in the table.

[0008] Also, input/output control corresponding to a plurality of peripheral control devices having a common peripheral device under their control and a processing device having these plurality of peripheral control devices under their control and connected to any one of the plurality of processing devices. In a loosely-coupled computer system equipped with a processing device, each processing device is provided with the above-described table, input/output path selection means, and input/output execution means.

[0009]

[Operation] In the input/output load distribution control method of the present invention,
A table provided in the processing unit stores load information for each peripheral control device (for example, the number of unprocessed I/O requests obtained by subtracting the number of completed I/O requests from the number of I/O requests accepted by each peripheral control device). , and information regarding the peripheral control device that used each peripheral device immediately before, and when an input/output request is made from an input/output request program, the input/output path selection means provided in the processing device retains in the table. Select an input/output path by referring to load information and last used peripheral control device information. At this time, if there are multiple peripheral control devices available for the peripheral device that is the target of input/output, and there is a difference in their loads, the input/output path that includes the peripheral control device with the smaller load will be selected. If there is no difference in load, an input/output path that includes a peripheral control device other than the peripheral control device that used the peripheral device immediately before is selected. Then,
The input/output execution means provided in the processing device starts input/output operations to the peripheral device via the input/output path selected by the input/output path selection means, and also transmits the load information and the most recently used peripheral control device information in the table. Update.

0010

Embodiments Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention. In the figure, a device group 14 is an input/output related device included in a computer system to which the input/output load distribution control method of this embodiment is applied, including one or more input/output control devices 141 and a plurality of peripheral control devices 142. and a plurality of peripheral devices 143.

The input/output request program 10 is a program that requests input/output to the peripheral device 143 in the device group 14, and is a program that requests input/output to the peripheral device 143 in the device group 14, and is a program that requests input/output from the peripheral device 143 in the device group 14. It works.

In addition, the input/output path selection means 11, the input/output execution means 12, and the input/output path management table 13 are components of the input/output load distribution control method of this embodiment, and the operating system running on the processing device constitutes part of.

The input/output path management table 13 is a table that holds various information necessary for selecting input/output paths (route), etc. In this embodiment, the configuration information 131, IOP (
It holds input/output control unit) load information 132, PCU (peripheral control unit) load information 133, and last used PCU information 134.

The configuration information 131 indicates the connection configuration between the peripheral device 143, the peripheral control device 142, and the input/output control device 141, and what kind of peripheral control device is connected to the upper level of each peripheral device, It is also information indicating what kind of input/output control device is connected to the upper level of each peripheral control device.

The IOP load information 132 is information indicating which input/output control device was used immediately before, and stores ON information corresponding to the device name of the input/output control device used immediately before, for example. Others store OFF information.

The PCU load information 133 is information indicating the load state of each peripheral control device, and in this embodiment, the number of input/output requests that have been processed is subtracted from the number of input/output requests accepted by each peripheral control device. Stores the number of unprocessed I/O requests.

The most recently used PCU information 134 is information indicating, for each peripheral device, which peripheral control device was used immediately for that peripheral device regarding input/output to the peripheral device; for example, the peripheral control device used immediately before. ON information is stored corresponding to the device name of the device, and OFF information is stored for the others.

The input/output path selection means 11 is means for selecting an input/output path to a peripheral device for which input/output is requested by the input/output request program 10 by referring to information in the input/output path management table 13. When selecting this input/output path, by using the internal PCU load distribution processing unit 111 and IOP load distribution processing unit 112, input/output paths are selected so that the load is not biased towards specific peripheral control devices and input/output control devices. Make a path selection.

Based on the configuration information 131, PCU load information 133, and last used PCU information 134 of the input/output path management table 13, the PCU load distribution processing unit 111 distributes the load so that the load is not biased toward a specific peripheral control device. This is the part in which the peripheral control device to be used is decided based on the above considerations, and an example of this process is shown in FIG.

Referring to FIG. 2, the PCU load distribution processing unit 111 executes the following steps.

Step 21; Input/output request program 10
The peripheral control device that has the peripheral device specified in is confirmed from the configuration information 131 of the input/output path management table 13.

Step 22: Based on the result of step 21, it is checked whether there are a plurality of usable peripheral control devices.

Step 23; When it is determined that there are a plurality of peripheral control devices that can be used, the load status of each peripheral control device is stored in P of the input/output path management table 13.
Check with the CU load information 133.

Step 24: When it is determined that there is only one peripheral control device available, that peripheral control device is determined as the peripheral control device to be used in the current input/output operation.

Step 25: Compare the load states of each peripheral control device based on the results of step 23.

Step 26; If the load states of the peripheral control devices match or if they are both in a no-load state, the peripheral control device used immediately before is set as the input/output path for the peripheral device that is the input/output target. Last used P of management table 13
Check from the CU information 134.

Step 28: A peripheral control device other than the peripheral control device used immediately before obtained in step 26 is determined as the peripheral control device to be used in the current input/output operation.

Step 27: When it is determined in step 25 that the load states do not match, the peripheral control device with the lightest load is determined as the peripheral control device to be used in the current input/output operation.

Next, the IOP load distribution processing unit 112 shown in FIG.
The determination is made based on the configuration information No. 3 and the IOP load information 132, and an example of the process is shown in FIG.

Referring to FIG. 3, the IOP load distribution processing unit 112 executes the following steps.

Step 31; PCU load distribution processing section 11
The input/output control device connected above the peripheral control device determined in step 1 is confirmed from the configuration information 131 in the input/output path management table 13.

Step 32: Based on the result of step 31, it is checked whether there are a plurality of usable input/output control devices.

Step 33; When there are a plurality of usable input/output control devices, the load status of these input/output control devices is determined by IOP load information 1 in the input/output path management table 13.
Check on 32.

Step 34: Based on the load status of each input/output control device confirmed in step 33, the input/output control device to be used in the current input/output operation is determined in a round robin manner.

Step 35: When there is only one input/output control device available, it is determined as the input/output control device to be used in the current input/output operation.

Step 36; Input/output control device of step 34 or step 3 determined by round robin method
The IOP load information 132 of the input/output path management table 13 is updated based on the input/output control device determined in step 5.

Next, the input/output execution means 12 in FIG. 1 is means for performing input/output operations on the peripheral device using the input/output path selected by the input/output path selection means 11 and updating the input/output path management table 13. An example of the processing is shown in FIG.

Referring to FIG. 4, the input/output execution means 12 executes the following steps.

Step 41: Add one input/output to the load status held in the PCU load information 133 of the input/output path management table 13 corresponding to the peripheral control device determined by the input/output path selection means 11. .

Step 42: The input/output path selection means 11 determines the information held in the most recently used PCU information 134 of the input/output path management table 13 corresponding to the peripheral device that is the target of the input/output request. Update to a new peripheral control device.

Step 43: The input/output path selected by the input/output path selection means 11 is used to perform input/output operations on the peripheral device.

Step 44: When the input/output execution operation is completed, the load state held in the PCU load information 133 of the input/output path management table 13 corresponding to the peripheral control device used for the current input/output execution is set to 1. Subtract only the input/output amount.

Next, the operation of the input/output load distribution control system of this embodiment configured as described above will be explained below with reference to FIG. 5 showing a specific example of the device group 14 of FIG. 1.

Note that FIG. 5 shows an example in which the present invention is applied to a loosely coupled computer system, which is composed of a first host A and a second host B. And the first host A
The processing unit (including central processing unit, main memory, etc.) a has 2
Two input/output control devices 511 and 512 are connected, and one input/output control device 513 is connected to the processing device b (also including a central processing unit, main memory, etc.) of the second host B. In addition, there are four peripheral control devices 521 to 524, and the peripheral control device 521 is the input/output control device 511, 512.
The peripheral control device 522 is connected to the input/output control device 51
The peripheral control device 523 is connected to the input/output control device 511, 513, and the peripheral control device 524 is connected to the input/output control device 511, 513.
are connected to input/output control devices 512 and 513. Further, common peripheral devices 531 and 532 are connected under the peripheral control devices 521 and 522, and the peripheral control device 523
, 524 are connected with common peripheral devices 533 and 534.

The input/output path selection means 11, input/output execution means 12, and input/output path management table 13 shown in FIG. are provided separately, and each processing device a,
Processes input/output requests from programs such as the input/output request program 10 of FIG. 1 running on B.

FIGS. 6 to 8 all show examples of the contents of the input/output path management table 13 provided in the first host A, and FIG. 6 shows input/output to the peripheral device 533 in the first host A. 7 shows the state immediately before, FIG. 7 shows the state at the time when the input/output is performed, and FIG. 8 shows the state at the time when the input/output to the peripheral device 534 is performed in the state of FIG.

FIGS. 9 and 10 also show that the second host B
9 shows the state immediately before input/output to the peripheral device 533 is performed on the second host B, and FIG. 10 shows the state at the time when the input/output is performed. The status of each is shown below.

First, the operation of the first host A will be explained with reference to FIGS. 6 to 8.

Before the first host A performs input/output to the peripheral device 533, as shown in FIG.
The OP load information indicates that the input/output control device 511 was used for the previous input/output (note that the input/output control device 513 is exclusive to the second host B, so it cannot be used), and
CU load information is provided by peripheral control devices 521, 522, 523,
It shows that the load status of 524 is load 1, load 3, load 1, load 0, and the peripheral devices 531,..., 533, 534
The peripheral control device that was used immediately before is the peripheral control device 522,
..., 524, 524.

In the state shown in FIG. 6, when an input/output request to the peripheral device 533 is issued from the input/output request program running on the processing device a, the input/output path selection means 11 on the processing device a is activated. , the input/output path for the current input/output request is selected as follows.

First, the input/output path selection means 11 determines the peripheral control device to be used by performing the processing shown in FIG. 2 by the PCU load distribution processing section 111. In this case, it is confirmed in steps 21 and 22 of FIG. 2 that two peripheral control devices 523 and 524 exist above the peripheral device 533 based on the configuration information in the input/output path management table shown in FIG. In steps 23 and 25, it is confirmed from the PCU load information that the load state of the peripheral control device 524 (load 0) is smaller than the load state of the peripheral control device 523 (load 1), and in the next step 27, it is confirmed that the load state of the peripheral control device 524 (load 0) is smaller than the load state (load 1) of the peripheral control device Control device 524
is determined as the peripheral control device to be used in the current input/output operation.

Next, the input/output path selection means 11 determines the input/output control device to be used by performing the processing shown in FIG. 3 by the IOP load distribution processing section 112. In this case, according to the configuration information in the input/output path management table in FIG.
Peripheral control device 52 determined by U load distribution processing unit 111
It turns out that there are two input/output control devices 512 and 513 above host No.4, but the IOP load information shows that the input/output control device 513 is exclusive to the second host B and cannot be used by the first host A. From this, it is determined in steps 31 and 32 of FIG. 3 that there is only one usable input/output control device, and in the next step 35, that input/output control device
12 is determined as the input/output control device to be used in the current input/output operation. Then, in the next step 36, the load state corresponding to the input/output control device 511 in the input/output path management table of FIG. 6 is switched from ON to OFF, and the load state corresponding to the input/output control device 512 is switched from OFF to ON ( (See Figure 7).

The input/output path selection means 11 includes the above-mentioned PCU load distribution processing section 111 and IOP load distribution processing section 112.
Based on the determination, the input/output control device 512 and the peripheral control device 5 are set as input/output paths for the peripheral device 533 this time.
Select the path via 24 and input it to input/output execution means 1.
Notify 2.

The input/output execution means 12 starts the process shown in FIG. 4, and first in step 41 updates the load state corresponding to the peripheral control device 524 from load 0 to load 1 (see FIG. 7). Further, in the next step 42, the immediately used PCU information corresponding to the peripheral device 533 is set to be the peripheral control device 524. In this case, since this is originally the case in Figure 6,
There are no substantial changes (see Figure 7). Next, step 43
This causes the peripheral device 533 to start an input/output operation using the selected input/output path. Note that when the input/output operation for the peripheral device 533 is completed, the load state is subtracted by one input/output (step 44), but it is assumed that the input/output is not yet completed at the time of FIGS. 7 and 8. Therefore, the load status remains at load 1 in both cases.

Now, in the state shown in FIG. 7, if an input/output request program running on the processing device a requests input/output to the peripheral device 534, the input/output path selection means 11 on the processing device a is activated again. and the input/output path selection means 11
First, the peripheral control device to be used is determined by performing the processing shown in FIG. 2 by the PCU load distribution processing unit 111. In this case, in steps 21 and 22 of FIG. 2, the configuration information in the input/output path management table shown in FIG.
It is confirmed that there are two peripheral control devices 523 and 524 at the upper level of No. 4, and in the next step 23 and 25, it is determined from the PCU load information that the load states of both peripheral control devices 523 and 524 are equal at load 1. Confirmed and next step 2
In step 6, it is confirmed that the peripheral control device that used the peripheral device 534 immediately before was the peripheral control device 524 based on the most recently used PCU information corresponding to the peripheral device 534, and in the next step 28, Peripheral control device 523
is determined as the peripheral control device to be used in the current input/output operation.

Next, the input/output path selection means 11 determines the input/output control device to be used by performing the processing shown in FIG. 3 by the IOP load distribution processing section 112. In this case, according to the configuration information in the input/output path management table in FIG.
Peripheral control device 52 determined by U load distribution processing unit 111
It turns out that there are two input/output control devices 511 and 513 above host No.3, but the IOP load information shows that the input/output control device 513 is exclusive to the second host B and cannot be used by the first host A. From this, it is determined in steps 31 and 32 of FIG. 3 that there is only one usable input/output control device, and in the next step 35, that input/output control device
11 is determined as the input/output control device to be used in the current input/output operation. Then, in the next step 36, the load state corresponding to the input/output control device 511 in the input/output path management table of FIG. 7 is switched from OFF to ON, and the load state corresponding to the input/output control device 512 is switched from ON to OFF ( (See Figure 8).

The input/output path selection means 11 includes the above-mentioned PCU load distribution processing section 111 and IOP load distribution processing section 112.
Based on the determination, the input/output control device 511 and the peripheral control device 5 are selected as input/output paths for the peripheral device 534 this time.
Select the path via 23 and input it to input/output execution means 1.
Notify 2.

The input/output execution means 12 performs step 4 in FIG.
Step 1 updates the load status corresponding to the peripheral control device 523 from load 1 to load 2 (see FIG. 8), and in the next step 42, the immediately used PCU information corresponding to the peripheral device 534 becomes the peripheral control device 523. (See Figure 8). Next, in step 43, input/output operations are activated for the peripheral device 534 using the selected input/output path. In addition, peripheral device 5
When the input/output operation for 34 is completed, its load state is subtracted by one input/output (step 44).

Next, the operation on the second host B side will be explained with reference to FIGS. 9 and 10.

Before input/output to the peripheral device 533 is performed in the second host B, as shown in FIG.
The OP load information indicates that the input/output control device 513 was used for the previous input/output (in addition, the input/output control device 511,
512 is exclusive to the first host A, so it cannot be used), the PCU load information is stored in the peripheral control devices 522, 523,
Indicates that the load status of 524 is load 3, load 0, load 0 (the peripheral control device 521 is unusable), and the peripheral control device 531, ..., 533, 534 is the peripheral control device that was used immediately before. are the peripheral control devices 522,..., 523,
524.

In the state shown in FIG. 9, when an input/output request to the peripheral device 533 is issued from the input/output request program running on the processing device b, the input/output path selection means 11 on the processing device b is activated. , the input/output path for the current input/output request is determined as follows.

First, the input/output path selection means 11 determines the peripheral control device to be used by performing the processing shown in FIG. 2 by the PCU load distribution processing section 111. In this case, it is confirmed in steps 21 and 22 of FIG. 2 that two peripheral control devices 523 and 524 exist above the peripheral device 533 based on the configuration information in the input/output path management table shown in FIG. In steps 23 and 25, it is confirmed based on the PCU load information that the loads of both peripheral control devices 523 and 524 are equal to 0, and in the next step 26, the peripheral device 533 is set to the last used PCU information corresponding to the peripheral device 533. It is confirmed that the peripheral control device used was the peripheral control device 523, and in the next step 28, the peripheral control device 52
A peripheral control device 524 different from No. 3 is determined as the peripheral control device to be used in the current input/output operation.

Next, the input/output path selection means 11 determines the input/output control device to be used by performing the processing shown in FIG. 3 by the IOP load distribution processing section 112. In this case, according to the configuration information in the input/output path management table in FIG.
Peripheral control device 52 determined by U load distribution processing unit 111
It turns out that there are two input/output control devices 512 and 513 above host No. 4, but the input/output control device 512 is exclusive to the first host A and cannot be used by the second host B.
In steps 31 and 32 of FIG. 3, it is determined that there is only one input/output control device that can be used, and in the next step 35, that input/output control device 513 is determined as the input/output control device to be used in the current input/output operation. . Then, in the next step 36, the input/output control device 5 in the input/output path management table of FIG.
The load state corresponding to 13 is turned ON. In this case, it is originally ON, so there is no substantial change (see Figure 10).
.

The input/output path selection means 11 includes the above-mentioned PCU load distribution processing section 111 and IOP load distribution processing section 112.
Based on the determination, the input/output control device 513 and the peripheral control device 5 are set as input/output paths for the peripheral device 533 this time.
Select the path via 24 and input it to input/output execution means 1.
Notify 2.

The input/output execution means 12 performs step 4 in FIG.
In step 1, the load state corresponding to the peripheral control device 524 is updated from load 0 to load 1 (see FIG. 10), and in the next step 42, the immediately used PCU information corresponding to the peripheral device 533 is updated to be the peripheral control device 524. (See Figure 10). next,
In step 43, input/output operations are activated for the peripheral device 533 using the selected input/output path. Note that when the input/output operation for the peripheral device 533 is completed, the load state is subtracted by one input/output (step 44).

[0066]

Effects of the Invention As explained above, the input/output load distribution control method of the present invention uses the control method for each peripheral control as a selection criterion when there are multiple peripheral control devices capable of controlling peripheral devices that are input/output targets. In addition to the load information of the device, information about the peripheral control device that used the peripheral device immediately before is adopted, and if the load is the same or there is no load, the peripheral control device other than the peripheral control device that used the peripheral device immediately before is used. , even if an input/output request to the peripheral device is issued from a single input/output request program, the load will not be biased to a specific peripheral control device.

[0067] Also, from other loosely connected processing devices, a single input/output request program can be sent to another peripheral device connected to the peripheral control device being used by the own processing device, in the same way as the own processing device. Even when a single input/output request is made, the same load distribution control as that of the own processing device is performed on the other processing devices, so that the load is not biased only on a specific peripheral control device. Therefore, it is possible to prevent competition between processing devices for a specific peripheral control device as much as possible, and to prevent a decline in input/output performance.

[Brief explanation of the drawing]

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

FIG. 2 is a flowchart illustrating an example of processing by a PCU load distribution processing unit 111.

FIG. 3 is a flowchart illustrating an example of processing by the IOP load distribution processing unit 112.

FIG. 4 is a flowchart showing an example of processing of the input/output execution means 12.

5 is a block diagram showing a specific example of the device group 14 in FIG. 1. FIG.

FIG. 6 is a diagram illustrating an example of the contents of an input/output path management table of the first host A.

7 is a diagram showing an example of the contents of the input/output path management table of the first host A at the time when input/output to the peripheral device 533 is performed in the state of FIG. 6. FIG.

8 is a diagram showing an example of the contents of the input/output path management table of the first host A at the time when input/output to the peripheral device 534 is performed in the state of FIG. 7. FIG.

FIG. 9 is a diagram illustrating an example of the contents of an input/output path management table of a second host B;

10 is a diagram showing an example of the contents of the input/output path management table of the second host B at the time when input/output to the peripheral device 533 is performed in the state of FIG. 9. FIG.

[Explanation of symbols]

10...I/O request program 11...I/O path selection means 111...PCU load distribution processing unit 112...IOP load distribution processing unit 12...I/O execution means 13...I/O path management table 131...Configuration information 132...IOP load information 133...PCU load information 134...Previously used PCU information 14...Device group 141...I/O control device 142...Peripheral control device 143...Peripheral device

Claims (2)

[Claims] Claim 1: In a computer system comprising a plurality of peripheral control devices having a common peripheral device under their control, and an input/output control device having the plurality of peripheral control devices under their control and connected to a processing device, A table that holds the load information of the control device and the last used peripheral control device information of the peripheral device, and the load information and the last used peripheral control device information held in the table at the time of an input/output request from the input/output request program are referenced. input/output path selection means for selecting an input/output path; and input/output operation for a peripheral device via the input/output path selected by the input/output path selection means; An input/output load distribution control method, characterized in that the processing device includes an input/output execution means for updating control device information. Claim 2: A plurality of peripheral control devices having a common peripheral device under their control, and an input/output corresponding to a processing device having the plurality of peripheral control devices under their control and connected to any one of the plurality of processing devices. In a loosely coupled computer system equipped with a control device, there is a table that holds load information of the peripheral control device and information of the peripheral control device most recently used for the peripheral device, and a table that holds the load information of the peripheral control device and the last used peripheral control device information of the peripheral device; Input/output path selection means for selecting an input/output path by referring to load information and last used peripheral control device information; and input/output operations for peripheral devices via the input/output path selected by the input/output path selection means. 1. An input/output load distribution control method, comprising: an input/output execution means for activating the table and updating the load information and the most recently used peripheral control device information for each of the processing devices.