JPH0132539B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a terminal session swapping control method in a time sharing system.

(Prior Art) In a time sharing system (hereinafter abbreviated as TSS), processing typically proceeds as follows. That is, a user inputs a command or data from a terminal and sends it to the processor at the center. The processor at the center processes the transmitted command or data and transmits the results to the terminal. The terminal user looks at the results displayed on the terminal, thinks about the command and data to input next, and inputs this from the keyboard, and the process is repeated.

Here, the process from inputting commands and data to the processor at the center, processing them, and outputting the results to a terminal is called a transaction. Furthermore, the time between transactions, that is, the time spent waiting for input from the terminal, is called wait time.
Furthermore, the substance of transaction execution at one terminal is called a session. This is equivalent to a job in the batch system.

Regarding a single session, as mentioned above, it usually takes several tens of seconds for the terminal user to look at the results displayed on the terminal from the center processor, think about the next data or command to input, and input it from the keyboard. While ordering takes time,
Processing by the center processor in response to commands input from the terminal is normally completed within a few seconds, the result is output to the terminal, and the next input from the terminal is awaited. Therefore, from the perspective of the center processor, most of the session time is wait time for the terminal user to think and input from the keyboard, and during this time the session program is kept in the main memory of the processor. This wastes the resources of the computer system, so a technique called swapping is generally used. This is done when the processing in the processor is completed, the result is displayed on the terminal, and the state is waiting for the next input (hereinafter referred to as the terminal input waiting state) (hereinafter referred to as the end of the transaction). The program to which it belongs is expelled from main memory to secondary memory (hereinafter referred to as swapout), and when the input from the terminal user is completed and processing by the processor is possible (hereinafter referred to as the start of a transaction). The session program is taken into main memory (hereinafter referred to as a swap-in). As a result, programs in each session only need to allocate main memory when they require processing by the processor. It is possible to support both at the same time.

In this way, it is common practice in TSS to use main memory efficiently and support a large number of terminals by performing swap-in when a transaction starts and swap-out when the transaction ends. .

However, if you are using a normal terminal that inputs input from the keyboard, thinking and subsequent keyboard input are required between the end of the transaction and the start of the transaction. In general, there is enough time to execute other sessions during this time, but for example, when data is continuously input to the center from a floppy disk on the terminal side, Because the time from when the processor issues an input request (transaction end) until data actually comes in from the terminal (transaction start) is very short, conventional swapping control methods do not allow the transaction to end. If you swap out, you will immediately need to swap in again, which not only does not free up space in main memory, but also increases the usage rate of the secondary storage disk, which reduces the throughput of the entire system. There are drawbacks.

For this reason, for example, you can measure the wait time of each session, and if it is smaller than a certain threshold, you can assume that the subsequent wait time will be short and avoid swapping out at the end of the transaction. Bye. however,
For example, if a case occurs where the operator leaves the terminal while inputting data from the floppy disk 7 and does not operate the terminal for a long time after completing the input, this session is a process that should be executed for a long time. Although it is not available, it occupies a part of the main memory, which has the disadvantage of lowering the overall throughput and prolonging the response time of other sessions.

(Objective of the Invention) The present invention measures the waiting time from the end to the start of a transaction for each session, and if the measured time is smaller than a set threshold value, the wait time from the end to the start of the transaction is By assuming that the wait time is short and not issuing a request for swapping out this session, unnecessary swapping can be omitted and swapping overhead can be reduced when continuous data is input from the terminal. At the same time, at regular intervals, the processor time used by the sessions in that cycle is checked, and if a session has not been processed at all in one cycle, this session is swapped out as an error in the wait time prediction. This aims to make effective use of main memory.

Therefore, the first object of the present invention is to improve the continuous input speed by omitting unnecessary swapping in continuous input, and the second object of the present invention is to increase the throughput of the TSS as a whole by reducing the swapping overhead. A third object of the present invention is to provide an improvement in which when swapping is omitted by predicting the wait time, even if the prediction is incorrect, this does not affect system throughput and response time. The purpose of the present invention is to provide a swapping control method for TSS.

(Structure of the Invention) The method of the present invention is a time sharing system in which a session corresponding to the terminal is swapped out when waiting for an input from the terminal, and a session corresponding to the terminal is swapped in when data input from the terminal is triggered. In a swapping control method for a ring system, a wait time measuring means for measuring a wait time from the end of a preceding first transaction in a session to the start of a second transaction following the first transaction; comparing means for comparing the measured wait time with a predetermined value and holding the result; and when the comparison result of the comparison means is smaller than the predetermined value, the second transaction is Swap-out prohibition means for prohibiting swap-out upon termination, and checking the processor usage time within the fixed cycle of each session in the swap-in state at regular intervals, and if the usage time is 0, swap-out is prohibited by the swap-out prohibition means. The session includes processor usage time check swap-out instructing means for instructing swap-out.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. The swapping control system shown in FIG. 1 includes a swapping control table 1, a session number register 2, a timer 3, a subtraction circuit 4, and a comparison circuit 5.
, a threshold register 6 , a transaction control section 7 , a swapping execution control section 8 , a session monitoring section 9 , an interrupt timer 10 , and a comparison circuit 1
1.

Swapping control table 1 is for controlling whether or not swapping is performed for each session. This table has one entry for each session, and each entry contains a time field XTIME to remember the time the previous transaction ended, a flag field F to indicate whether or not to swap out for this session, and a previous check field. A time field that holds the session's processor usage time in a cycle.
Has PTIME. This swapping control table 1 is addressed by the session number j in which a transaction start/end occurs and the session number j generated by the session monitoring section 9.
The session number register 2 holds the session number j where the transaction start/end occurred.

The value of the timer 3, which holds the current time, is applied to one input of the subtraction circuit 4, and is also applied to the time field XTIME of the swapping control table 1. Also the time field XTIME
The output of is applied to the other input of the subtraction circuit 4, and this output is applied to one input of the comparison circuit 5. The threshold register 6 is a register that holds the threshold value of the wait time, and its output is applied to the other input of the comparator circuit 5.
The output of the comparison circuit 5 is applied to the transaction control section 7. The output of the time field PTIME of the swapping control table 1 is applied to one input of the comparison circuit 11. The other input of comparison circuit 11 receives the current processor time of each session. This processor time is read from a session control table (not shown) that manages the status of all sessions in use by the processor. Each entry in the session control table contains information indicating whether the corresponding session is swapped in or not, and the cumulative amount of processor time used by the corresponding session to date.
CTIME is stored. The transaction control unit 7 receives event notifications X _S and X _T of transaction start and end in each session,
This is a control unit that measures the wait time in each session and compares it with a threshold value to determine whether or not to perform swap-in at the start of swap-out at the end of a transaction. The swapping execution control unit 8 is a control unit that performs actual swap-in and swap-out according to commands from the transaction control unit 7.
The interrupt timer 10 is a timer for activating the session monitoring section 9 at fixed intervals (here, 30 seconds). The session monitoring unit 9 is a control unit that checks the status and processor usage time of each session at regular intervals to detect errors in wait time measurement.

FIG. 2 is an operational flowchart of FIG. 1.
Figure 2a shows the operation at the start of a transaction, Figure 2b shows the operation at the end of the transaction, and Figure 2b shows the operation at the end of the transaction.
Figure c shows the operation of periodic transaction monitoring.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 and 2. When terminal input is completed in a certain session j and the processor is ready for processing, that is, at the start of a transaction, this notification X _S is first applied to the transaction control unit 7, and the session number j is Applied to session number register 2. The transaction control unit 7 receives this notification and performs the following processing. That is, first, the session number j is stored in the session number register 2, and then the entry corresponding to the session number j in the swapping control table 1 and the timer 3 are read out. The value of the time field XTIME and the value of the timer 3 read at this time are applied to a subtraction circuit 4, and the result is applied to a comparison circuit 5. Comparison circuit 5 compares the value with threshold value register 6 . Note that the value of the flag field Fj is temporarily saved (the save location is not shown). As a result of the comparison, if the threshold is larger, that is, if the wait time from the end of the transaction to the start is shorter than the threshold, swap out should be prohibited at the end of the next transaction. In order to indicate this, "1" is set in the flag field Fj corresponding to the session j of the swapping control table 1. Otherwise, the value "0" is set.

After this, the value of the flag field Fj that was read earlier is checked, and if this is "0", that is, swap-out has been performed at the end of the previous transaction, swap-in of this session is performed. This swap-in is performed by issuing a command to the swapping execution control section 8. If the value of the previously read flag field Fj is "1", that is, if swap-out has not been performed, swap-in is not necessary, and the processing for transaction control ends.

At the end of the transaction, a transaction end notification X _T is applied to the transaction control unit 7, the session number j is set in the session number register 2, and the value of the timer 3 is read out and stored in the swapping control table 1. is stored in the corresponding time field XTIMEj.

After this, read the flag field Fj and set it to “1”
If so, that is, if the previous wait time is smaller than the threshold value, the transaction control processing is ended without swapping out. Fj
If the value of is "0", the corresponding session is swapped out.

Next, a process for detecting errors in waiting time prediction will be explained.

When the interrupt timer 10 sends a notification to the session monitoring section 9 at regular intervals, the session monitoring section 9 performs the following operations.

First, the following processing is performed for all sessions that are currently connected to terminals. That is, it reads the corresponding entry in the session control table to determine whether this session is swapped in. If it is in the swap-in state, read the corresponding entry in swapping control table 1 and set the read time field.
A comparison circuit 11 compares the value of PTIMEj, that is, the processor time at the time of the previous interrupt, and the value of the field CTIME of the accumulation time of the session control table, that is, the processor time at the present time. At this time, it is checked whether the value of the time field PTIME is invalid, and if it is invalid, it is regarded as a mismatch.

If the values match, that is, if no processing related to this session has been executed in the processor since the previous interrupt, check the flag field F of the swapping control table 1. If it is "1", that is, the wait time is If the swap-out is omitted due to the prediction that the session will be short, it is determined that this prediction was wrong, and the swapping execution control unit 8 is instructed to swap out this session, and the time field of the swapping control table 1 is written as follows. Accumulation time field
Set and update the value of CTIME. If there is a mismatch, update PTIME. If the swap-in state is not established, a flag is set in the time field PTIME to indicate that the value of the time field PTIME is invalid at the next check.

In the description of this embodiment, in order to simplify the explanation, descriptions of parts that are not directly related to the gist of the present invention are omitted. Furthermore, detailed explanations of how to implement the transaction control unit, swapping control unit, session monitoring unit, and session control table are omitted;
These can be realized by conventionally known methods.

It is clear that the present invention is not limited to the configuration of the embodiment. For example, the session number register 2, the threshold register 6, etc. do not necessarily need to be provided with special hardware as registers, and are stored in the main memory. It is also possible to have a storage area above. The same applies to the subtraction circuit 4, the comparison circuit 5, etc., and it is clear that it is not necessarily necessary to provide dedicated hardware for controlling the above-mentioned swapping.

(Effects of the Invention) The present invention measures the wait time for each session, and if the wait time is smaller than a set threshold value, the swap-out of this session is prohibited, and if the swap-out prohibition is erroneous, the swap-out of this session is prohibited. Also, by checking the processor time used in a session at regular intervals, the errors can be corrected and the throughput of the system can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
2a, b and c are flowcharts showing the operation of FIG. 1. DESCRIPTION OF SYMBOLS 1... Swapping control table, 2... Session number register, 3... Timer, 4... Subtraction circuit, 5... Comparison circuit, 6... Threshold register, 7... Transaction control section, 8... Swapping execution control unit, 9... session monitoring unit,
10...Interrupt timer.

Claims (1)

[Claims] 1 In a swapping control method of a time sharing system, a session corresponding to the terminal is swapped out when waiting for an input from the terminal, and a session corresponding to the terminal is swapped in when data input from the terminal is triggered. the first preceding in
a wait time measuring means for measuring a wait time from the end of a transaction to the start of a second transaction following the first transaction; and a result of comparing the measured wait time with a predetermined value. swap-out prohibition means for inhibiting swap-out at the end of the second transaction if the comparison result of the comparison means is smaller than the predetermined value; Checks the processor usage time within the fixed cycle for each session in the swap-in state and specifies swap-out for sessions whose usage time is 0 and swap-out is prohibited by the swap-out prohibition means. 1. A swapping control method comprising: out instruction means.