Space optimization method for priority bitmap algorithm

An optimization method and priority technology, applied in the direction of multi-programming devices, etc., can solve the problems of PBA space complexity, PBA expansion dilemma, PBA scheduling time-consuming increase, deterioration of PBA real-time scheduling performance, etc., to improve real-time scheduling capabilities, Reduce the time-consuming effect of the algorithm

Inactive Publication Date: 2011-04-13
SOUTHWEST JIAOTONG UNIV
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  • Application Information

AI Technical Summary

Problems solved by technology

[0027](3): The space complexity of PBA and the expansion dilemma of PBA
[0054] In summary, although Document A and Document B reduce the space complexity of PBA to a certain extent, these improvements are based on the complexity of the table lookup process , PBA scheduling time-consuming increase at the expense of deterioration of the real-time scheduling performance of PBA to a certain extent

Method used

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  • Space optimization method for priority bitmap algorithm
  • Space optimization method for priority bitmap algorithm
  • Space optimization method for priority bitmap algorithm

Examples

Experimental program
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Effect test

Embodiment 1

[0080] Table 4

[0081] So alternative combinational logic circuits are:

[0082]

[0083]

[0084] .

[0085] Example 2:

Embodiment 2

[0087] table 5

[0088] So alternative combinational logic circuits are:

[0089]

[0090]

[0091]

[0092] The equivalence statement of replacing the priority decision table with a combinational logic circuit:

[0093] A 7 ~A 0

[0094] Table 6

[0095] Therefore B k Must be an OR of m signals. Since the high-priority task automatically shields the low-priority task, the m signals must be the "AND" of several signals in the form. Right now:

[0096] Among them, ,, ..., are those integers whose k-th bit is 1 among 0~n-1 in binary representation. And the above algorithm happens to be able to calculate any B k The m "A x ":,,...,.

[0097] The PBA space optimization method disclosed by the present invention replaces the priority judgment table OSUnMapTbl with a combinational logic circuit, and abandons the table lookup process for the priority judgment table OSUnMapTbl, so that the space complexity of PBA is reduced to O(1). Combination logic...

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Abstract

The invention discloses a space optimization method for a priority bitmap algorithm (PBA). In an embedded system, the method supports multi-priority and multi-task real-time scheduling and is characterized in that: a priority decision table is substituted by a combined logic circuit. In the method, the priority decision table OSUnMapTb1 is substituted by the combined logic circuit according to determinacy on a content of the priority decision table OSUnMapTb1, an address signal for reading data from the OSUnMapTb1 by using the original PBA and read data are mapped to be an input signal and anoutput signal of the combined logic circuit respectively, and the scheduling time consumption is reduced and the real-time scheduling capacity of the PBA is improved while the space complexity of thePBA is reduced to be O(I) by the method.

Description

technical field [0001] The invention belongs to embedded system application, especially the technical field of real-time scheduling algorithm. Background technique [0002] Priority Bitmap Algorithm (PBA-Priority Bitmap Algorithm) is a key algorithm that supports multi-priority and multi-tasking in embedded operating systems. stable scheduling. The characteristic of PBA is: for a certain priority scale, the time-consuming of the PBA algorithm is a fixed value, that is, it has nothing to do with the number of tasks in the ready queue, which enables PBA to ensure that the search process for the highest priority task is completed within a certain time , avoiding uncertainty about the response time of real-time tasks. The disadvantage of PBA is that the space complexity is too high, which makes it very expensive to expand PBA to support more priorities, and even impossible to achieve in extreme cases. [0003] The PBA in supports up to 64 tasks with different priorities, with...

Claims

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Application Information

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IPC IPC(8): G06F9/46
Inventor申志军曾华燊
OwnerSOUTHWEST JIAOTONG UNIV