CN102103549A

CN102103549A - Method for replacing cache

Info

Publication number: CN102103549A
Application number: CN2009102013772A
Authority: CN
Inventors: 王永流
Original assignee: Shanghai Huahong Integrated Circuit Co Ltd
Current assignee: Shanghai Huahong Integrated Circuit Co Ltd
Priority date: 2009-12-18
Filing date: 2009-12-18
Publication date: 2011-06-22

Abstract

The invention relates to a method for replacing a cache. The method comprising the following steps of: setting an auxiliary cache, wherein the auxiliary cache and the cache jointly participate in data storage; testing the hit of a read cache; if the miss of the read cache occurs, transmitting an external memory read request and temporarily storing data which are written back into the auxiliary cache; after the read request is transmitted, writing data in the auxiliary cache back to an external memory; and if the miss of the read cache and the hit of the auxiliary cache occur, only copying the data to the cache from the auxiliary cache without transmitting the external memory read request. Due to the adoption of a method for setting the auxiliary cache, invalid waiting time in the data reading process can be effectively reduced, and the operating performance of an application system can be improved, so that the power consumption of the system can be effectively reduced.

Description

A kind of buffer replacing method

Technical field

The present invention relates to a kind of data cache method, relate in particular to the replacement method that a kind of integrated circuit is used the high speed buffer memory.

Background technology

Nowadays multimedia technology has obtained general application in daily life, more and more higher in the part multimedia application to the requirement of image accelerating module and CPU processing speed, and the problem of the processing speed of current these unit substantially all is limited in above the read-write external memory storage.

Can adopt high-speed cache for satisfying the integrated circuit application, the current cache mode probably can be divided into three kinds from using: a kind of is read-only buffer memory; A kind of is the buffer memory of only writing, and another is a buffer memory not only readable but also that can write.What this part content related to is last a kind of buffer memory form: the readable buffer memory of writing.When occurring reading cache miss when (being called for short " miss "), need write back to external memory storage earlier, and then send the request of reading external memory storage being write (being called for short " dirty ") part.The module of request for data need be waited for the memory write request time like this, read request time and data read back the time.Consider other processing times of moderator, storage unit controller, conservative estimation needs 50 clock period to read back needed data at least, and read-write can occur alternately, and the frequency that replaces can be very high.Long and the inaccurate problem of data read of elapsed time can appear in the metadata cache processing procedure like this.

At the problems referred to above, a kind of new caching solution need to be proposed, can reduce the data read stand-by period, when guaranteeing operating performance, save power consumption.

Summary of the invention

The object of the invention provides a kind of buffer replacing method, reduces the invalid stand-by period in the data read process, improves the application system runnability, reduces system power dissipation.

The present invention relates to a kind of buffer replacing method, comprise following content:

(1) auxiliary cache is set, auxiliary cache and buffer memory fellowship data storage;

(2) read the cache hit test, read cache miss, send the external memory storage request of reading, temporary in auxiliary cache the data that write back simultaneously;

(3) after read request distributes, the data in the auxiliary cache are write back to external memory storage;

(4) if read cache miss, in auxiliary cache, hit, do not need to send and read the external memory storage request and only need from auxiliary cache copies data in buffer memory.

An auxiliary cache is set, and the data that needs are write back are temporarily stored in the auxiliary cache, and read request can be sent at once like this, otherwise corresponding data such as needs write back to external memory storage earlier, make buffer memory discharge corresponding position, just can send read request.If before the position discharges, send read request, data of coming of reading back probably or can not be put into suitable position, otherwise will the data that needs write back have been covered.

Read request sends, and sends and writes application, can save and read the stand-by period.For writing, wait and bide one's time very unimportantly, but kind of a situation is arranged: when miss (read cache miss, be called for short miss) appears in the read request buffer memory, auxiliary cache hit (cache hit is called for short hit) need copy this content to buffer memory from auxiliary cache.Further reduce the carrying of data if desired, reduce the dynamic power consumption of integrated circuit, can allow buffer memory and auxiliary cache, the exchange role.When miss occurring, current cache becomes auxiliary cache, and current auxiliary cache becomes buffer memory, can solve the data carrying between buffer memory and the auxiliary cache.

From the realization of integrated circuit, adopt two independently storage unit than adopt a storage unit from area still be on the power consumption all greatly.Based on this reason, can merge to a storage unit to buffer memory and auxiliary cache, storage bit number is both sums, distinguishes buffer memory and auxiliary cache with the high address.

Adopt buffer memory alternative provided by the invention, can effectively reduce the invalid stand-by period in the data read process, improve the application system runnability, thereby can reduce system power dissipation effectively.

Description of drawings

Fig. 1 buffer memory and auxiliary cache are the structural representation of storer independently

Fig. 2 buffer memory and auxiliary cache are arranged at the structural representation of same storer

Embodiment

Below in conjunction with each accompanying drawing, the foregoing invention content is described in detail:

To be buffer memory and auxiliary cache be the situation of storer independently to Fig. 1.Suppose that buffer memory is divided into four parts, is respectively A, B, C, D; Auxiliary cache also is divided into four parts, is respectively A ', B ' C ', D ', and following three kinds of situations are arranged:

1, when new read request hit B in buffer memory, directly reading of data from B;

2, as new read request miss in buffer memory, corresponding position is C, also miss in auxiliary cache, and corresponding position is C ':

(1) data of reading among the C are write among the C ';

(2) send read the application;

(3) data among the C ' are write back to external memory storage (when bus is idle);

(4) data of reading back from external memory storage are write C;

(5) from C, read desired data;

3, new read request miss in buffer memory, corresponding position is D, hit in auxiliary cache, correspondence position are A ':

(1) data of reading A ' are write D;

(2) from D, read desired data.

Fig. 2 is arranged at same storer for buffer memory and auxiliary cache, and buffer memory and auxiliary cache can exchange, and supposes that buffer memory is divided into four parts, is respectively A, B, C, D; Auxiliary cache also is divided into four parts, is respectively A ', B ' C ', D ', and following several situation is arranged:

1, new read request hit B in buffer memory, direct reading of data from B, buffer memory and auxiliary cache role are constant;

2, new read request miss in buffer memory, corresponding position is C, also miss in auxiliary cache, corresponding position is C ':

(1) auxiliary cache C ' becomes buffer memory, and buffer memory C becomes auxiliary cache;

(2) send out read the application;

(3) content among the C writes back to external memory storage;

The data of (4) reading back are write among the C ';

(5) from C ', read desired data.

3, new read request miss in buffer memory, corresponding position is D, hit in auxiliary cache, correspondence position are A ', then:

(1) auxiliary cache A ' becomes buffer memory, and buffer memory D becomes auxiliary cache;

(2) from A ', read desired data;

(3) data write back to external memory storage among the D.

Claims

1. buffer replacing method comprises following content:

(2) read the cache hit test, when reading cache miss, send the external memory storage request of reading, temporary in auxiliary cache the data that write back simultaneously;

(4) if read cache miss, in auxiliary cache, hit, need not send the external memory storage request of reading, directly from auxiliary cache copies data in buffer memory.

2. a kind of buffer replacing method as claimed in claim 1 is characterized in that: described buffer memory saves as different storeies with auxiliary changing.

3. a kind of buffer replacing method as claimed in claim 1 is characterized in that: described buffer memory and auxiliary cache are arranged at same storer, and storage bit number is both sums.

4. as claim 1 or 3 described a kind of buffer replacing methods, it is characterized in that: described buffer memory and auxiliary cache can exchange, and adopt the high address to distinguish both.