JPH04127338A - Buffer managing system - Google Patents

Abstract

PURPOSE:To execute the pool management of an unused buffer area in a state that a real memory is not allocated fixedly by rejecting the real memory as for an unnecessary buffer pool, that is, setting it to a state that it is taken away easily by invalidating a reference/updating bit. CONSTITUTION:The system is provided with a real memory allocating device 1, a real memory rejecting device 2, and a buffer pool managing device 3. In such a state, at the time of opening a buffer area of a fixed state of a real memory, the real memory is set to a state that the real memory allocating device 1 can take away easily the real memory, that is, a state that the correspondence of a logical address - a real address can be detached easily by invalidating only a reference/updating bit on a page table by the real memory rejecting device 2 without opening the real memory, that is, without erasing an entry from the page table. In such a way, an unused buffer area is managed in a state that the real memory is not allocated fixedly.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Application Fields Conventional Technology and Means for Solving the Problems to be Solved by the Invention Examples of Effects and Problems of the Invention [Summary] Adopting a virtual memory system, Regarding a method for managing pools of unused buffer areas without fixedly allocating real memory in computer systems that do not allow page faults to occur, real memory is discarded for unnecessary buffer pools. By making it easy to take away, you can manage it without allocating real memory.
In addition, the purpose of this method is to provide a buffer management method that can quickly acquire a buffer with fixed real memory when necessary, and to self-manage a virtual memory area to which real memory is not allocated. Take the empty real memory that is currently in use, or the real memory that is allocated to the virtual memory area but has not been referenced or updated, from the virtual memory (by turning off the page table's hardbin l-(V)). ) assign (
Valid bit (ν) of another entry in the page table
A real memory allocation device that disables reference/update bits for virtual memory that is no longer needed in real memory allocation state, and a real memory discard device that manages buffer areas in page units. , When there is a request to acquire a buffer area, the buffer is cut out from the pool,
If it is an area to which real memory is not allocated to the extracted buffer, the real memory allocation device allocates real memory to the extracted buffer area, and in the area where real memory is allocated to the extracted buffer, If the reference/update bit is disabled in an area, the buffer is immediately acquired (the user program is notified), and when a request to return the buffer area is made, the buffer is returned and the buffer is returned. When all the pages in which the buffer exists are no longer needed ~ The above real memory discarding device disables the reference/update bits and discards the real memory by providing a buffer pool management device to discard the unused buffer area. The memory is configured to be managed in a state where it is not fixedly allocated, that is, in a state where it is not set as a working set.

[Industrial application field]

The present invention provides a computer system that uses a virtual memory method and has a state in which page faults are not allowed to occur.
This invention relates to a method for managing an unused buffer area in a pool without allocating real memory.

With the recent diversification of data processing in computer systems, the number of user programs executed under a system program is also increasing. We are in a situation where there are many requests.

In particular, in the case of a computer system that uses a virtual memory method and has a state in which page faults are not allowed, the real memory space must be fixed relative to the logical memory space. Then, there is a problem that unused real memory is pooled and the real memory space is compressed, that is, it becomes a working set.

Therefore, the overhead of acquiring and discarding the real memory can be reduced, and the real memory can be acquired quickly at the time of acquisition.
At the time of rejection, there is a need for a buffer management method that can efficiently manage the memory area by allocating real memory so that the return area does not become a working set, and thereby not compressing the memory area. be done.

[Prior art and problems to be solved by the invention] FIG. 3 is a diagram illustrating a conventional buffer management system.

In a computer system like the one shown in this figure, in which many user programs are executed under a system program, the user program uses resources (real memory) managed by the system program for the system program. In the case of such processing, the mechanism for acquiring a memory area (work area: buffer) executed by the system program in order to complete the requested processing has conventionally been performed as follows.

Because system programs - sometimes only execute one process - typically need to run in a state where page faults are not tolerated.

In such a computer system, the system program acquires an area in which real memory is fixed as the buffer.

In particular, when it is necessary to acquire the buffer at high speed, buffers whose real memory is fixed are managed in a pool to enable high-speed acquisition and return of the area.

When constructing area acquisition and return logic using such pool management, ■ In order to perform area acquisition and return processing at high speed, as mentioned above, there is always unused real memory in the pool. This means that there are many fixed buffers.

■ Due to numerous requests from user programs, - degrees,
When the pool management mechanism acquires a buffer whose real memory is in a fixed state (specifically, holds it in the pool) and allows the user program to use it, even if the user program returns it, the pool In order to keep the fixed memory of the real memory in the pool (i.e., in the conventional method, the data is stored from the user program so that it can immediately respond to subsequent requests from the user program). (There was no mechanism to discard returned buffers), the problem was that unused real memory gradually remained in the pool, increasing the possibility that the real memory area would be overwhelmed. Ta.

Of course, if the number of pools in the pool management mechanism becomes extremely large, the page table management mechanism (not shown) deletes specific entries in the page table, which will be described later.
Mechanisms exist to free real memory, so not all real memory is pooled. Further, the entry may be acquired if necessary.

By using this page table entry deletion and acquisition mechanism, it is possible to manage buffers in a state where real memory is not fixedly allocated, that is, to manage buffers that do not become working cents. However, it is necessary to perform the page table deletion and acquisition processing, which requires a large amount of processing time, and there is a problem in that the processing capacity of the computer system is significantly reduced.

In view of the above-mentioned conventional drawbacks, the present invention manages unused buffer areas in pools without fixedly allocating real memory, but discards real memory for unnecessary buffer pools. By disabling the reference/update bit to make it more likely to be stolen, real memory can be managed without being fixedly allocated (no working set), and real memory can be quickly allocated when needed. The object of the present invention is to provide a buffer management method that allows a buffer to be acquired in a fixed state.

[Means to solve the problem]

FIG. 1 is a diagram showing the basic configuration of the present invention.

The above problems are solved by a buffer management method configured as follows.

In a computer system that uses a virtual memory method and has a state in which the occurrence of page faults is not allowed, this method manages unused buffer areas in a pool without allocating real memory in a fixed manner. Empty real memory that is managed by the self for a virtual memory area that is not used, or real memory that is allocated to a virtual memory area but is not referenced or updated, the correspondence between virtual memory and real memory. Detach and assign (
That is, the real memory allocation device 1 sets the valid bit (v) of the corresponding entry in the page table to “on”.
and a real memory discarding device 2 that invalidates reference/update bits for virtual memory in a real memory allocation state that is no longer needed.

The real memory allocation device 1 manages the buffer area in page units, and when a buffer area acquisition request is received, it cuts out a buffer from the pool, and if the cut out buffer is an area to which no real memory has been allocated, the real memory allocation device 1 As soon as real memory is allocated to the extracted buffer area, if the above reference/update bit is disabled, the buffer is Acquired, notifies the user program, and when there is a request to return the buffer area, when all the pages in which the buffer exists are no longer needed due to the return of the buffer, the real memory discarding device 2 performs the following:
A buffer pool management device 3 that invalidates the reference/update bit and discards real memory is provided to manage unused buffer areas without fixedly allocating real memory.

[Operation] As is well known, in a computer system that uses a virtual memory method, a page table is used to establish a correspondence between a logical memory address and a real memory address, and a user program running within a vast logical address space is , allocating real memory space in pages.

In the page table, if the valid bit (V) is turned on, it indicates that the page of the real address is allocated to the corresponding logical address page, and the valid bit (v) is turned on. However, if the reference/update bit is ``off'', it indicates that the real memory of the page is not being used, at least not at that time.

The present invention particularly provides for such a computer system,
In computer systems that do not allow page faults to occur, unused buffer areas are pool-managed without allocating real memory in a fixed manner, in other words, without compressing the real memory area. , Empty real memory managed by the virtual memory area to which real memory has not been allocated (at the time of initialization of the computer system, or during the well-known real memory replenishment process (replacement process with a file device)) (Real memory secured)?

When the real memory no longer exists, it is allocated to the virtual memory area (that is, the valid bit (v) on the page table is “on”), but
For real memory that has not been referenced or updated (that is, the reference/update bit is "off"), the correspondence between virtual memory and real memory is separated, that is, the valid bit (V) of the corresponding entry in the page table is set. Assign it to another logical address requested by the user program (in other words, turn on the valid bit (V) of the other corresponding entry in the page table).
) with a real memory allocation device.

The reference/update bits on the above page table are applied to the virtual memory that is no longer needed in the real memory allocation state (the reference/update bits are not necessarily on the above page table; for example, the reference/update bits are not necessarily on the real memory ) and a real memory rejection device that invalidates the memory.

The buffer area is managed on a page-by-page basis, and when a request to acquire a buffer area is received from a user program,
If a buffer (logical address area) is extracted from the pool and the extracted buffer is an area to which no real memory has been allocated, the real memory allocation device will assign the extracted buffer area to the free state managed by itself. Allocate real memory, turn on the valid bit (V) of the corresponding entry in the page table, and disable the reference/update bit above when real memory is allocated to the extracted buffer (logical address area). If the area is set to , the buffer will be immediately acquired (passed to the user program), and when there is a request to return the buffer area, the page where the buffer exists will be restored by returning the buffer. A buffer pool management device is provided which discards the real memory by invalidating the reference/update bit using the real memory discarding device when all of the memory is no longer needed, and the unused buffer area is used as an entry in the page table. In contrast to this, real memory is managed without being fixedly allocated.

That is, when releasing a fixed state buffer area of real memory, the real memory discarding device does not explicitly release the real memory, that is, erase the entry from the page table (erase the entry). Nosan W! , / Only the update bit is disabled, and the real memory allocation device is in a state where it is easy to take over the real memory (valid bit (V) is "off",
The overhead of the real memory return processing is eliminated by setting the memory to a state that is easy to turn on.

Therefore, according to the buffer management method of the present invention, unnecessary buffers are pooled by discarding real memory, that is, by invalidating the reference/update bits on the page table.
A state in which the real memory allocation device is likely to take away the real memory, that is, a state in which it is easy to separate the correspondence between logical addresses and real addresses and create a different correspondence relationship, and a state in which real memory is not fixedly allocated; In other words, it is possible to manage a pool of buffers without creating a working set, and when real memory is needed, in most cases it is sufficient to acquire real memory with the reference/update bit set to OFF. Even if the real memory is not allocated, the real memory managed by the real memory allocation device is immediately allocated to the logical page requested by the user program, that is, the real memory is allocated to the corresponding entry in the page table. As you can allocate it and set its valid bit (V) to 'on',
This method has the advantage of being able to acquire a buffer in a fixed state in real memory at a speed comparable to that of the conventional method.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

The above-mentioned FIG. 1 is a diagram showing the principle configuration of the present invention, and FIG. 2 is a diagram showing an embodiment of the present invention, in which (a) shows an example of the configuration of a buffer pool management device, and (b) (c) schematically shows the operation when a buffer acquisition request is made, and (c) schematically shows the operation when a buffer return request is made.

In this embodiment, a real memory allocation device 1, a real memory discard device 2. When the buffer pool management device 3 is provided to release a fixed buffer area in real memory, the real memory is explicitly discarded without releasing the real memory, that is, without deleting the entry from the page table. By invalidating only the reference/update bits on the page table in the device 2 and making it easy for the real memory allocation device 1 to steal real memory, that is, to make it easy to separate the correspondence between logical addresses and real addresses, A means necessary to carry out the present invention is a means for fixedly allocating memory to buffers and managing the buffer pool without putting pressure on real memory, that is, without causing working cents. Note that the same reference numerals indicate the same objects throughout the figures.

Hereinafter, the buffer management system of the present invention will be explained with reference to FIG. 2 while referring to FIG.

First, the buffer pool management device 3 pool-manages the buffers with the real memory removed, that is, the logical address space, so in the memory space where the real memory is fixed, as shown in FIG. Use a queue structure management table.

The management table includes, for example, the buffer management header, next address (address pointer), and buffer address.
(pool start address), pool size, etc.

The buffer pool is an area in units of pages or units of multiple pages in consideration of allocation/disposal of real memory.

The above management table is sufficient compared to the buffer pool.
Since it can be done with a small area, it does not become a working cent for buffer pool management. That is, it does not occupy a wide range of real memory and pressure the real memory area.

The real memory allocation device 1 allocates free real memory to a virtual memory area (buffer) to which no real memory is allocated, without generating a page fault, and executes the virtual memory area (buffer). It is a device that keeps the memory in a fixed state, and the real memory to be allocated is either free real memory managed by the real memory allocation device, that is, real memory secured at the time of initializing the computer system mentioned above, or Alternatively, if the real memory runs out, the real memory that has been allocated to the virtual memory area but has not been referenced or updated, that is, neither the reference bit nor the update bit is set, is replaced with the virtual memory. It is taken from the area and, specifically, is used by turning off the valid bit (v) on the page table.

Therefore, the real memory allocation device l is a device that allocates truly free real memory to buffers, and conventional buffer pool management devices fixedly allocate real memory to buffers acquired once. This is a fundamentally different allocation mechanism from holding data while it is allocated and compressing the real memory area.

In addition, the real memory discarding device 2 stores virtual memory in the real memory allocation state that is returned from the user program and is no longer needed (
This is a device that makes it easy for the real memory allocation device 1 to allocate a buffer by simply invalidating its reference/update bit, and is a feature of the present invention.

In this device 2, the real memory is not actively removed from the virtual memory, that is, the valid bit (V) on the page table is not turned off.
Processing that only performs reference/update bit operations on the page table and actually takes away real memory, specifically, processing that eliminates the logical memory address - real memory address pair from the page table (specifically, As described above, since the process of turning off the valid bit (V) is left to the real memory allocation device, real memory can be discarded at high speed.

In the buffer pool management device 3 configured as described above,
The operation when acquiring and discarding a buffer will be explained below.

1) Buffer acquisition processing = (b) See figure When a buffer acquisition request is made to the buffer pool management device 3 from the user program, the buffer pool management device 3 cuts out the buffer from the pool.

At this time, if real memory is not allocated to the extracted buffer, that is, if the valid bit (V) of the corresponding logical address space (in page units) is "off" on the page table, A real memory allocation request is sent to the real memory allocation device l of the present invention.

At this time, in the conventional method, a page fault would occur, but in the present invention, the occurrence of the page fault is suppressed and the real memory allocation device 1 is requested to allocate real memory.

As mentioned above, the real memory allocation device 1 allocates the free real memory managed by the real memory allocation device 1.
That is, the page address of the real memory is written to the corresponding entry in the page table, and its valid bit (v) is set to "on", but when the free real memory runs out, the page address is allocated to the virtual memory area. That is,
The valid bit (V) on the page table is on, but the real memory that has not been referenced or updated, that is, the real memory where the reference/update bit is off, is stolen from the page table, That is, the above valid bit (V
) is set to "off" and passed to the buffer pool management device 3.

The buffer pool management device 3 allocates the transferred real memory to the buffer requested by the user program. Specifically, the buffer pool management device 3 assigns the page address of the stolen real memory to another corresponding entry in the page table. By writing the data and turning the valid bit (V) on, the buffer acquisition process is completed.

2) Buffer return processing = (C) See figure When a user program requests the buffer pool management device 3 to return a buffer, the buffer pool management device 3 returns the buffer to the pool.

For example, if all of a certain page (provided that the pool can pool multiple pages) in the buffer pool is in a returned state, the real memory rejecting device 2 of the present invention Request processing.

The real memory rejection device 2 that has received the rejection request performs the reference/removal on the page table corresponding to the pooled buffer.
By disabling (“off”) the update bit, the real memory becomes
The real memory is simply put in a state where it is easy to be taken by the real memory allocation device 1, and the process of actively removing the real memory (the process of turning off the valid bit (v) on the page table) is not performed.

Therefore, the rejection process can be performed at high speed.

In this way, in a computer system that uses a virtual memory method and exists in a state where the occurrence of page faults is not allowed, the conventional buffer pool management device actively manages the real memory when the real memory is returned from the user program. As mentioned above, since no processing such as rejection was performed,
In the pool, buffers to which real memory is fixedly allocated are held, which puts pressure on the real memory area, that is, creates a state of working cents. In the buffer management method, the real memory discarding device turns off the reference/update bits of buffers that have been returned from the user program and is no longer needed, and when a buffer request is received from the user program, the real memory discarding device In response to a request from the management device 1, the real memory allocation device 1 sets the above reference/update bit to “only when there is no free real memory that it manages.”
It takes the real memory that is off, that is, turns off the valid bin lm of the corresponding page table, passes it to the buffer pool management device, allocates it to the requested logical address space, and stores the corresponding memory on the page table. Since the valid bit of the entry is turned on, the real memory space is not fixed to a specific logical address space and is not held as a working set. be.

[Effects of the Invention] As explained above in detail, the buffer management method of the present invention uses a virtual memory method and is capable of managing unused buffer areas in a computer system in which a page fault order is not allowed. In order to manage the pool without allocating memory in a fixed manner, the virtual memory area (buffer) to which real memory has not been allocated is either an empty real memory managed by itself or a virtual memory area. A real memory allocation device that allocates real memory that has been allocated but has not been referenced or updated from virtual memory (by turning off valid pits (V) on the page table), and real memory allocation that is no longer needed. A real memory discard device that disables reference/update bits for state virtual memory, and a real memory discard device that manages buffer areas in page units, and when a buffer area acquisition request is received, a buffer is cut out from the pool and the corresponding If the extracted buffer is an area to which real memory has not been allocated, the real memory allocation device allocates real memory to the extracted buffer area (valid bit of the corresponding entry in the page table).
V) is turned on), as soon as real memory is allocated to the extracted buffer, if the above reference/update bit is disabled, the buffer is immediately acquired. , is passed to the user program, and when there is a request to return the buffer area, when the buffer is returned and all the pages where the buffer exists are no longer needed, the real memory discard device clears the reference/update bits. This system is equipped with a buffer pool management device that discards real memory by invalidating it, and manages unused buffer areas without permanently allocating real memory. , By simply discarding the real memory, that is, invalidating the reference/update bit on the page table, the real memory allocation device is in a state where it is easy to take away the real memory, that is, the correspondence between logical address and real address is separated, It is easy to use a different correspondence relationship, and the buffer pool can be managed without fixed allocation of real memory, that is, without a working set, and when real memory is needed, most of the time In this case, it is sufficient to acquire the real memory whose reference/update bit is off', and even if no real memory has been allocated, it is sufficient to allocate the real memory managed by the real memory allocation device, and the corresponding Even if there is no real memory managed by real memory,
Since the real memory with the reference/update bit "off" can be taken and allocated to the logical page requested by the user program, the real memory fixed state can be allocated at a speed comparable to that of conventional methods. It has the effect of allowing you to acquire a buffer.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle configuration of the present invention. FIG. 2 is a diagram showing an embodiment of the present invention. FIG. 3 is a diagram explaining a conventional buffer management method. It is. In the drawing, 1 is a real memory allocation device, and 2 is a real memory discard device. 3 is a buffer pool management device. are shown respectively. system program No. figure No. figure (Part 1) No. figure (Part 2)

Claims (1)

[Scope of Claim] A method for managing an unused buffer area in a pool without allocating real memory in a fixed manner in a computer system that uses a virtual memory method and has a state in which the occurrence of page faults is not allowed. , Empty real memory that is managed by itself for a virtual memory area to which no real memory is allocated, or real memory that is allocated to a virtual memory area but is not referenced or updated. A real memory allocation device (1) that separates the correspondence between virtual memory and real memory and allocates it; and a real memory discard device (2) that invalidates reference/update bits for virtual memory that is no longer needed in a real memory allocation state.
), the buffer area is managed in page units, and when a buffer area acquisition request is received, a buffer is cut out from the pool, and if the cut out buffer is an area to which real memory is not allocated, the real memory is Allocation device (1)
As soon as real memory is allocated to the extracted buffer area, if the above reference/update bit is disabled, the buffer is When there is a request to return the buffer area, the real memory discard device (2) clears the reference/update bits when all the pages in which the buffer exists are no longer needed due to the return of the buffer. A buffer management method characterized by comprising: a buffer pool management device (3) that discards real memory by invalidating it, and manages an unused buffer area without fixedly allocating real memory.