JP2636484B2 - Buffer management method - Google Patents

Description

Detailed Description of the Invention [Table of Contents] Overview Industrial application field Conventional technology and problems to be solved by the invention Means to solve the problem Action Embodiment Effect of the invention [Overview] Take virtual storage method, In a computer system that has a state in which page faults are not allowed to occur, a method of pool management of unused buffer areas without permanently allocating real memory. Regarding unnecessary buffer pools, reject real memory. By making it easy to be deprived, it can be managed without allocating real memory, and when necessary,
The purpose of the present invention is to provide a buffer management method in which a real memory can acquire a buffer in a fixed state at a high speed. Either memory (free real memory that is neither in the pool nor on the page table) or real memory allocated to the virtual memory area but not referenced / updated from the virtual memory Take it, {set the valid bit (V) of the page table to 'off', {assign it}, set the valid bit (V) of another entry of the page table to 'on', {real memory allocation device and real A real memory rejection device that invalidates the reference / update bit for the virtual memory in the memory allocation state and a buffer area acquisition request that manages the buffer area in page units and requests a buffer area acquisition request When there is a buffer, the buffer is cut out from the pool, and if the real memory is not allocated to the cut out buffer, the real memory allocation device allocates real memory to the cut out buffer area, and If the reference / update bit is invalidated while the real memory is allocated to the buffer, the buffer is acquired {notified to the user program} and the request for the buffer area return request is made. A buffer pool management device for invalidating the reference / update bit and rejecting the real memory by the real memory rejecting device when all the pages in the buffer become unnecessary by returning the buffer. In a state where the unused buffer area is not fixedly allocated to the real memory, that is, the state in which the real memory can be easily reused. In other words, the management is performed in a state that does not become a working set.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of pool management of unused buffer areas in a computer system having a virtual memory system and having a state in which a page fault is not allowed to occur without allocating real memory. .

With the recent diversification of data processing by computer systems, the number of user programs executed under the control of system programs has also been increasing, and acquisition and rejection of common resources managed by the system programs, for example, real memory, have been increasing. There are many requests.

In particular, in the case of a computer system that employs a virtual memory system and has a state in which page faults are not allowed, it is necessary that the real memory space be fixed with respect to the logical memory space. Then, there is a problem that the unused real memory is pooled and the real memory space is squeezed, that is, it becomes a working set.

Therefore, real memory can be acquired at high speed at the time of acquisition by reducing the overhead of the acquisition and rejection processing of the real memory, and at the time of rejection, the return area does not become a working set. There is a need for a buffer management method that can efficiently manage a memory area without squeezing the area.

[Problems to be solved by conventional technology and invention]

FIG. 3 is a diagram for explaining a conventional buffer management system.

Under the system program as shown in this figure,
In a computer system in which many user programs are executed, when a user program uses a resource (real memory) managed by the system program for the system program, the requested process is executed. Conventionally, a mechanism for acquiring a memory area (work area: buffer) for executing the system program has been performed as described below.

Since the system program executes only one process at a time, it is usually necessary to run in a state where a page fault is not allowed.

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

In particular, when it is necessary to obtain the buffer at high speed, the buffer in which the real memory is in a fixed state is pool-managed, and high-speed area acquisition and return are enabled.

When the area acquisition / return logic is constructed by such pool management, the area is always unused, but the real memory is fixed in the pool, as described above, in order to perform the area acquisition / return processing at high speed. A large number of state buffers exist.

Due to many requests from the user program, once
When the pool management mechanism acquires a buffer in which the real memory is in a fixed state (specifically, holds the buffer in the pool) and permits the user program to use the buffer, even if there is a return from the user program, the pool In order to keep the fixed buffer of the real memory in the pool within the pool (that is, in the conventional method, the buffer is returned from the user program so that it can immediately respond to a subsequent request from the user program). There was no mechanism for rejecting the buffer), and there was a problem that unused real memory was gradually kept in the pool, and the possibility of pressing down the real memory area was increased.

Of course, when the number of pools in the pool management mechanism becomes extremely large, there is a mechanism that a page table management mechanism (not shown) deletes a specific entry of a page table described later and releases real memory. Therefore, not all real memory is pooled. Also, the entry may be obtained as needed.

By using this page table entry erasure and acquisition mechanism, buffer management in a state in which real memory is not fixedly allocated, that is, in a state in which real memory is easily reused, that is, buffer management that does not become a working set However, for that purpose, it is necessary to execute the erasure and acquisition processing of the page table which requires a lot of processing time, and there is a problem that the processing capacity of the computer system is significantly reduced. .

In view of the above-mentioned conventional disadvantages, the present invention manages an unused buffer area in a pool without real memory being fixedly allocated, and rejects the real memory for an unnecessary buffer pool, that is, By invalidating the reference / update bit to make the state easy to be deprived, it is possible to manage the real memory in a state where it is not fixedly allocated, that is, in a state where the real memory is easily reused (a state that does not become a working set). It is another object of the present invention to provide a buffer management method that can acquire a buffer in which a real memory has a fixed state at a high speed when necessary.

[Means for solving the problem]

 FIG. 1 is a diagram showing the principle of the present invention.

The above problem is solved by a buffer management system configured as follows.

In a computer system using a virtual storage method and having a state in which page faults are not allowed to occur, unused buffer areas are pooled in a state in which real memory is not fixedly allocated, that is, in a state in which real memory is easily reused. This is a management method in which the real memory in the free state which is allocated to the virtual memory area to which the real memory is not allocated (the free real memory which does not exist in the pool nor exists in the page table). (Real memory) or a real memory that has been allocated to the virtual memory area but has not been referenced / updated, and is allocated by separating the virtual memory-real memory correspondence. The valid bit (v) of the real memory allocation device 1 to “on”. Real memory rejection device 2 for invalidating update bit
When there is a request for a buffer area acquisition request in units of pages, the buffer is cut out from the pool, and if the real memory is not assigned to the cut out buffer, the real memory allocating device 1 By
A real memory is allocated to the cut buffer area, and if the reference / update bit is invalid while the real memory is allocated to the cut buffer, the buffer is acquired as it is. When a request for a buffer area return request is made, when the buffer is returned and all pages in which the buffer is present become unnecessary, the real memory rejection device 2 A buffer pool management device 3 which invalidates the / update bit and rejects the real memory is provided, and the inactive buffer area is not fixedly allocated to the real memory, that is, the real memory is easily reused. Configure to manage.

[Action]

As is well known, in a computer system using a virtual memory system, a page table is used to associate a logical memory address with a real memory address, and a user program running in a large logical address space is page-by-page. Real memory space is allocated.

In the page table, when the valid bit (V) is “ON”, it indicates that the page of the real address is allocated to the relevant logical address page, and the valid bit (V) is “ON”. Even so, if the reference / update bit is 'off', it indicates that the real memory of the page is at least unused at that time.

The present invention relates to such a computer system, particularly, in a computer system having a state in which the occurrence of a page fault is not allowed, in a state in which an unused buffer area is not fixedly allocated with real memory, that is, a real memory area is allocated. The pool is managed without pressure, so for that,
A free real memory secured by itself for a virtual memory area to which no real memory is allocated (a free real memory that is neither in the pool nor on the page table) ｛the computer system At the time of initialization of the real memory, the real memory secured by a known real memory replenishment process (replacement process with a file device), or when the real memory no longer exists, the real memory is allocated to the virtual memory area. For a real memory in which the valid bit (V) on the table is 'on' but not referenced / updated (ie, the reference / update bit is 'off'),
The correspondence between the virtual memory and the real memory is separated, that is,
The valid bit (V) of the corresponding entry in the page table is set to "OFF" and the logical address is allocated to another logical address requested to be allocated by the user program. That is, the valid bit (V) of another corresponding entry in the page table is assigned.
Is turned on. The reference / update bit on the page table (the reference / update bit is not necessarily And the memory may be added to the real memory, for example.) And a real memory rejecting device that invalidates the buffer area, manages the buffer area in units of pages, and receives a request from the user program to acquire the buffer area. When a request is made, a buffer (logical address area) is cut out from the pool, and if the cut out buffer is an area to which no real memory has been allocated, the real memory allocating apparatus assigns itself to the cut out buffer area. Allocate the reserved free real memory (free real memory that is neither in the pool nor in the page table) The valid bit (V) of the corresponding entry of the page table is set to “ON”, and the extracted buffer (logical address area)
If the reference / update bit is invalidated while the real memory is allocated to the area, the buffer is acquired (passed to the user program) and the request for the buffer area return request is received. When there is, when all the pages in which the buffer exists become unnecessary by returning the buffer, by the real memory rejection device,
A buffer pool management device that invalidates the reference / update bit and rejects the real memory is provided, and an unused buffer area is fixedly allocated to the real memory while keeping the entry of the page table as it is. In this case, the real memory is managed in a state where it is not available, that is, the real memory is easily reused.

That is, when the buffer area in the fixed state of the real memory is released, the real memory is explicitly released, that is, the real memory discarding device does not delete the entry from the page table (delete the entry). By invalidating only the reference / update bit of the real memory, the real memory allocating device puts the real memory in an easy-to-take-off state (a state in which the valid bit (V) is easily turned off and on). This is to eliminate the overhead of the memory return processing.

Therefore, according to the buffer management system of the present invention, the real memory is discarded when pooling unnecessary buffers, that is, the reference / update bit on the page table is invalidated, so that the real memory allocation device can A state in which real memory is easily robbed,
That is, the correspondence between the logical address and the real address is separated,
In a state where it is easy to make another correspondence, a state where real memory is not fixedly allocated, that is, a state in which a working set is not established, buffer pool management can be performed, and
When real memory is required, in most cases, real memory with the above-mentioned reference / update bit set to “off” can be obtained. Even if the real memory is not allocated, the real memory allocation device manages the real memory. The real memory is immediately allocated to the logical page requested by the user program, that is, the real memory is allocated to the corresponding entry of the page table, and the valid bit (V) can be turned on. Therefore, there is an effect that a buffer in a real memory fixed state can be obtained at a speed not inferior to the conventional method.

〔Example〕

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, (a) shows a configuration example of a buffer pool management device, and (b) 5 schematically shows an operation at the time of a buffer acquisition request, (c) schematically shows an operation at the time of a buffer return request, and (d) shows a configuration example of a pool.

In the present embodiment, when the real memory allocating device 1, the real memory rejecting device 2, and the buffer pool management device 3 are provided to release the buffer area in the fixed state of the real memory, the real memory is explicitly released. That is, without deleting entries from the page table, the real memory rejection device 2
Disable only the reference / update bit of the page table,
A state in which the real memory allocation device 1 easily takes over real memory, that is,
By making the correspondence between the logical address and the real address easy to separate, the real memory is fixedly allocated to the buffer,
Means for performing buffer pool management that does not squeeze real memory, that is, does not become a working set, is a means necessary for implementing the present invention. Note that the same reference numerals indicate the same object throughout the drawings.

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

Clarify the relationship between pools, buffers, and pages used in the following description. That is, a page is the smallest unit of real memory allocated to virtual memory, and a buffer is
The unit of real memory when acquiring / returning virtual memory.
The size of the page may be larger or smaller than that of the page, and the size of the page may be different for each user / requester.

And pool (sometimes called buffer pool)
Is a continuous relatively large virtual area for allocating the buffer, and the buffer is obtained by cutting out an area of a predetermined size from the pool and allocating it on the page table. When there is no sufficient free virtual area in the pool to allocate the buffer, a new pool is searched for a page table to allocate real memory, and the new real memory is allocated. Buffer from the pool. A virtual area not allocated as a buffer in the pool is rejected in page units.

Also, even if the real memory is allocated to the virtual memory, if it is neither referenced nor updated, it can be considered as an unused state immediately after the real memory allocation, and this real memory is stored in the above-described page table. Even if the relationship between the real memory and the virtual memory is cut off and the virtual memory is allocated to another virtual memory, this does not affect the user program. Therefore, this state is referred to as rejection of the real memory.

First, the buffer pool management device 3 manages the buffer in a state where the real memory is removed, that is, in the memory space where the real memory is fixed in order to perform pool management of the logical address space, as shown in FIG. Use a queue structure management table.

The management table includes, for example, a buffer management header, a header address (address pointer), a buffer address (head address of a pool), a pool size, and the like.

The buffer pool is an area in units of pages or a plurality of pages in consideration of allocation / rejection of real memory.

Since the management table described above can be completed in a small area sufficiently compared with the buffer pool, it does not become a working set for buffer pool management. That is, the real memory is not occupied over a wide area, and the real memory area is not pressed.

The real memory allocation device 1 allocates an empty real memory to a virtual memory area to which no real memory is allocated, that is, a buffer without causing a page fault, and allocates the virtual memory area (buffer) to the real memory area. The real memory to be allocated is a real memory to be allocated, and the real memory to be allocated is an empty real memory managed by the real memory allocation device, that is, the real memory secured at the time of initialization of the computer system or the like. Alternatively, when the real memory is exhausted, it is allocated to the virtual memory area,
The real memory in which neither reference nor update is performed, that is, neither the reference bit nor the update bit is set is taken from the virtual memory area, and specifically, the valid bit (V) on the page table is set to ' Use 'off'.

Therefore, the real memory allocating device 1 is a device that allocates a real free real memory to a buffer, and the real buffer allocating device 1 allocates a real memory to a buffer acquired once by a conventional buffer pool management device. Holding as it is and compressing the real memory area means having a fundamentally different allocation mechanism.

Further, the real memory rejection device 2 simply invalidates the reference / update bit for the virtual memory (buffer) returned from the user program and no longer required in the real memory allocation state, thereby realizing the real memory allocation. The device 1 is a device that makes the device 1 easily rob, and characterizes the present invention.

The device 2 actively removes the real memory from the virtual memory. That is, the valid bit (V) on the page table is not turned off, and
A process of actually performing only reference / update bit operations on the page table and actually taking the real memory, specifically, a process of eliminating the logical memory address-real memory address pair from the page table. As described above, since the process of turning the valid bit (V) “off” is left to the real memory allocation device, the real memory can be rejected at high speed.

Buffer pool management device 3 configured as described above
The operation for acquiring and rejecting a buffer will be described below.

1) Buffer Acquisition Processing: (b) See FIG. 7 When a buffer acquisition request is made from the user program to the buffer pool management device 3, the buffer pool management device 3 cuts out the buffer from the pool.

At this time, when the real memory is not allocated to the cut-out buffer, that is, in the above-mentioned page table, the buffer in which the valid bit (V) of the corresponding logical address space (page unit) is “off” is stored in the buffer. Then, a real memory allocation request is sent to the real memory allocation device 1 of the present invention.

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

As described above, the real memory allocating device 1 allocates an empty real memory managed by the real memory allocating device 1, that is, writes the page address of the real memory in the corresponding entry of the page table, (V)
Although it is set to 'ON', when the empty real memory is exhausted, it is allocated to the virtual memory area, that is,
A real memory in which the valid bit (V) on the page table is “on” but is neither referenced nor updated, that is, a real memory whose reference / update bit is “off” is deprived from the page table. That is, the valid bit (V) is set to “OFF” and is passed to the buffer pool management device 3.

The buffer pool management device 3 allocates the passed real memory to the buffer requested by the user program. More specifically, the buffer pool management device 3 stores the page address of the stolen real memory in another corresponding entry of the page table. By writing and turning on the valid bit (V),
The buffer acquisition processing ends.

2) Buffer return processing: See (c) diagram When a buffer return request is made from the user program to the buffer pool management device 3, the buffer pool management device 3 returns the buffer to the pool.

In the buffer pool, for example, a certain page (however,
If the pool can pool multiple pages)
Are all returned, the real memory rejection device 2 of the present invention is requested to perform a rejection process.

Upon receiving the rejection request, the real memory rejection device 2 invalidates ('off') the reference / update bit on the page table corresponding to the pooled buffer, and the real memory is allocated to the real memory. The process of removing the real memory (the process of turning off the valid bit (V) on the page table) aggressively only by setting the device 1 to a state in which it is easily robbed is not performed. Therefore, the rejection processing can be performed at high speed.

FIG. 2 (d) shows that the real memory allocating apparatus 1 processes the “allocate the real memory secured by itself” in α of FIG. 2 (b) and the “reference / update bit is“ off ”in β. Shows the state of the pool at the time of executing the process "Stealing real memory from page table".

The buffer pool management device 3 attempts to allocate the area of a) in FIG. 2D as a buffer in response to a buffer acquisition request, but no real memory is allocated to the page by the method α. In other words, if there is no room in the real memory secured by itself, the real memory allocating apparatus 1 uses the method of β to store the real memory shown in c) of FIG. 2 (d). The deprivation {operation of the valid bit (V) on the page table} is allocated as the buffer real memory described above.

As described above, in the computer system that adopts the virtual storage method and has a state in which the occurrence of a page fault is not allowed, the conventional buffer pool management device aggressively returns the real memory from the user program when returning the real memory from the user program. Since processing such as rejection was not performed, as described above, the buffer in which the real memory is fixedly allocated is kept as it is, and the real memory area is pressed, that is, the working set and However, in the buffer management method of the present invention, the real memory discarding device turns off the reference / update bit of the unnecessary buffer returned from the user program. ', There is a buffer request from the user program, and in response to a request from the buffer pool Sets the reference / update bit to 'off' only when there is no more free real memory (free real memory that is neither in the pool nor in the page table) that it has secured. The real memory that has become invalid, that is, the valid bit (V) of the corresponding page table is set to 'off', passed to the buffer pool management device, allocated to the requested logical address space, and It operates so that the valid bit of the corresponding entry is set to 'ON', so that the real memory space is not retained as it is fixed in the specific logical address space, and does not become a working set. There is.

〔The invention's effect〕

As described above in detail, the buffer management method of the present invention employs a virtual storage method, and in a computer system having a state in which the occurrence of a page fault is not allowed, an unused buffer area is fixed to a real memory. Although pool management is performed in a state where no real memory is allocated, an empty real memory that is managed by itself for a virtual memory area (buffer) to which no real memory is allocated, or a virtual memory area that is allocated to a virtual memory area. A real memory that is not referenced / updated from the virtual memory, {assigns the valid bit (V) on the page table to “off”} and allocates the real memory, and the virtual memory in the unnecessary real memory allocation state In response to the request, a real memory rejection device that invalidates the reference / update bit and a buffer area acquisition request that manages the buffer area in page units If there is a buffer, the buffer is cut out from the pool, and if the real memory is not allocated to the cut-out buffer, the real memory is allocated by the real memory allocating device to the cut-out buffer area. Of the valid bit (V) is turned “on”. If the reference / update bit is invalid while the real memory is allocated to the extracted buffer, the buffer is left as it is. Is obtained and passed to the user program. When a request for a buffer area return request is made, when the page in which the buffer exists becomes unnecessary by returning the buffer, A buffer pool management device that invalidates the reference / update bit and rejects the real memory is provided, and the unused buffer area is stored in the real memory. Memory is not fixedly allocated, that is, the real memory is managed in an easy-to-reuse state. Therefore, for an unnecessary buffer, the real memory is rejected, that is, reference / By invalidating the update bit, the real memory allocating device is in a state where the real memory is easily robbed, that is, in a state where the correspondence between the logical address and the real address is easily separated and another correspondence is easily obtained. A state in which memory is not fixedly allocated, that is, a state in which real memory is easily reused,
That is, when the pool of buffers can be managed and the real memory is required in a state where it is not a working set, in most cases, only the real memory with the above-mentioned reference / update bit “off” needs to be acquired. Even if the real memory is not allocated, it is sufficient to allocate the real memory managed by the real memory allocating device. Even if there is no real memory managed by the real memory, the reference / update bit “off” is set. Can be allocated to a logical page requested by the user program, so that a buffer in a fixed state of real memory can be obtained at a speed comparable to that of the conventional method. effective.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is a diagram illustrating an embodiment of the present invention, and FIG. 3 is a diagram illustrating a conventional buffer management system. In the drawing, reference numeral 1 denotes a real memory allocation device, 2 denotes a real memory rejection device, and 3 denotes a buffer pool management device.

Claims (1)

(57) [Claims] In a computer system employing a virtual storage method and having a state in which page faults are not allowed to occur, a method of managing an unused buffer area in a pool in an easy-to-reuse state, wherein real memory is allocated. For a virtual memory area that has not been allocated, either the free real memory that has been allocated by itself, or
When the real memory is no longer present, the real memory that has been allocated to the virtual memory area but has not been referenced / updated is disconnected from the corresponding relationship of the virtual memory real memory, and the allocation request from the user program is issued. A real memory allocating device for allocating another logical address, a real memory rejecting device for invalidating only the above-mentioned reference / update bit for a virtual memory in an unnecessary real memory allocating state, and a page for a buffer area. When the user program requests the acquisition of the buffer area,
A buffer is cut out from the pool managed by itself, and if the cut out buffer is an area to which no real memory is allocated, the real memory allocation device uses the cut-out buffer area to allocate a free When the real memory in the state is allocated, or when the real memory no longer exists, the buffer is acquired for the real memory allocated to the virtual memory area but not referred / updated. When the buffer is allocated to another logical address for which allocation has been requested by the user program, and a request for a buffer area return request is made, when the buffer is returned and all pages in the buffer become unnecessary, A buffer pool management device for invalidating only the reference / update bit and rejecting the real memory is provided by a memory reject device. A buffer management method wherein unused buffer areas are managed in a state where they can be easily reused.