WO2001022233A2

WO2001022233A2 - Management of access rights to buses with dynamic priority regulation

Info

Publication number: WO2001022233A2
Application number: PCT/DE2000/003114
Authority: WO
Inventors: Andreas Staudigl; Gerhard Otte
Original assignee: Siemens Aktiengesellschaft
Priority date: 1999-09-17
Filing date: 2000-09-07
Publication date: 2001-03-29
Also published as: WO2001022233A3

Abstract

The aim of the invention is to more flexibly use bus resources. The possibility to dynamically design the priority allocation by a arbiter (1) is provided. The arbiter allocates access rights to bus resources to several users (1, 2, X). The waiting cycles (W1, W2, W3) of the individual users (1, 2, X) are evaluated (3). Priority is newly allocated (4) according to the evaluation. The priority allocation is brought back to the arbiter (1) by means of a feedback loop (5).

Description

description

Management of bus access rights with dynamic priority control

The present invention relates to a method and system for managing bus access rights for multiple users.

The present invention relates generally to the field of managing multiple subscriber access rights to a bus, also called arbitration. A bus arbiter manages access to the bus transmission medium for the various participants. Bus arbitration is therefore a decision logic that assigns the bus to the participants according to certain selection criteria. The bus arbiter thus determines whether or not a certain participant is granted access to the bus.

When using a bus arbiter in multiprocessor systems, an arbitration procedure with a fixed priority, such as the round robin procedure, is defined in advance. Temporary priority shifts are hardly possible.

A round-robin method is a technique in which each participant has access to the bus for a certain period of time and after this time the next participant is allocated an equally long access time. This fixed priority pattern thus functions satisfactorily in the case of priorities of equal rank.

It is also known from the prior art to grant an subscriber an exclusive bus access right via additional lines (hold, hold acknowledge). This completely bypasses the priority order. However, this is not a dynamic priority assignment. Based on the prior art mentioned, it is an object of the present invention to provide a technique for managing access rights (arbitration) of several participants on a bus, which technology can react dynamically to time-varying loads on the bus by the different participants.

According to the invention, this object is achieved by the features of the dependent claims. The independent claims further develop the central idea of the invention in a particularly advantageous manner.

According to the invention, a method for managing bus access rights for several subscribers is therefore provided. Priorities for the access of the participants to the bus are assigned according to a predetermined pattern. The waiting cycles of the individual participants, which result from the actual stress on the bus, are recorded and evaluated. Then the priorities for the access of the participants to the bus are dynamically changed (optimized) depending on the evaluation of the waiting cycles.

A waiting cycle is a cycle in which a subscriber is not assigned access to the bus despite issuing a request to the bus arbiter due to other, preferred requests.

The priorities can be optimized in such a way that access rights with a higher priority are allocated to participants with long waiting cycles compared to other participants.

The dynamic change of the priorities can only take place temporarily in the event that the waiting cycle of at least one participant exceeds a predetermined threshold. below. In addition, a fixed priority can be assigned according to the round robin technique, for example.

The priorities can be changed dynamically in such a way that the waiting cycles of the different participants are essentially balanced and, in the optimal case, regulated to zero.

According to a further aspect of the invention, a system for managing bus access rights for a plurality of subscribers is provided. An arbiter assigns priorities for the access of the participants to the bus according to a predetermined pattern, such as the round robin pattern. A priority control is also provided for recording and evaluating the waiting cycles of the individual participants, which are set by the participants as a result of the actual stress on the bus. The priority control gives changed priorities for the access of the participants to the bus depending on the evaluation of the waiting cycles to the arbiter. A priority control loop is thus provided to optimize the allocation of priority.

The priority control can change priorities to the arbiter in such a way that access rights with increased priority are allocated to participants with long waiting cycles compared to other participants.

The dynamic change of the priorities by means of the priority control can take place temporarily (only) in the event that the waiting cycle of at least one participant exceeds a predetermined threshold. In addition, the arbiter can carry out a fixed priority assignment comparable to the round robin technique.

Further features, advantages and properties will become apparent in the following with reference to an exemplary embodiment and the accompanying figure of the drawing. The figure schematically shows a bus arbitration with dynamic priority control according to the present invention.

As shown in the figure, an arbiter 1 is provided for managing bus access rights for a plurality of subscribers 1, 2, x. Participants 1, 2, x issue request signals Ctrl.l, Ctrl.2 or Ctrl.x to arbiter 1 in order to register an access request to the bus. Depending on the load on the bus, a waiting cycle Wi, W ₂ , W _x results for each of the participants 1, 2, _x . Waiting cycles result when several participants simultaneously send request signals to bus arbiter 1 and the arbiter 1 must decide on the basis of the current priority assignment which participant is granted access to the bus and which participant is only granted access to the bus after waiting cycles have expired ,

According to the invention, the current waiting cycles Wi, W ₂ , W _x , which are set by the bus load, are fed to a priority control unit 2. A waiting cycle evaluation unit 3 is provided in the priority control unit 2, which evaluates the supplied waiting cycles Wi, W ₂ , W _x and compares them with a threshold value. The detected and evaluated waiting cycles are fed to a priority allocation unit 4 in the priority control unit 2.

Depending on the detected and evaluated waiting cycles Wi, W ₂ , W _x , the priority assignment unit 4 assigns new priorities for the individual subscribers 1, 2, X and the priorities modified in this way are fed back to the arbiter 1 by a feedback loop 5.

The waiting cycle evaluation unit 3, the priority allocation unit 4 and the feedback loop 5 thus form a control loop for dynamic priority allocation, as a result of which the priority allocation can be constantly optimized in accordance with the actual bus load. The time constant and so- ) KJ t ¹ P »

Lπ o Lπ o Cn o Lπ r + r? rt tr 3

(D: α 3 P- 3 T) N 3 öd cn> v PH H) in rt tr α N to Φ ö z w 3

P. φ £ P- Φ H- H- H Φ P- Φ Ό H 3 = _^ o Φ p. P- ^ <Φ d Φ P- P-

P- hfl rt P ⁾ n Φ t Φ rt P- P- rt P- P- P- n 3 P- Φ φ \ * r Φ cn HH 3 rt

Φ o cn 3 cn P 3 rt φ o S? X P- o cn 3 n C n

P ι- (O ω 0 ⁾ Φ Φ ≤ Φ N Φ WH o cn rt r + tr Φ Φ rt Hl - Φ rt d α α φ Ό HH Φ H- P- N P- φ cn P- H P- N Φ 3 3 P d Φ 3 Φ P-

3 Φ HN tr H φ H- 3 ^• X5 3 CL ≤ rt 3 ndt S 3 φ φ P- α P ^J φ

M3 H and others d P- Φ rt Φ rt Φ P ⁾ φ p ^j : P> tr ⁾ Φ α N ^ ⁾ P ¹ P- P ¹

N d P> n rt n CS1 H a. Φ HH P- rt μ- ¹ rt l_l. 3 ι- (1 d O: iQ 3 φ d σ

Φ 3 tr tr H t 0 C- Φ P- Hi cn cn 1 P- φ 3 P_ 3 P- φ 3 • <yQ Φ Φ P- 3 ιQ σ SI H φ φ <yQ α φ 3 P- 3 φ P ¹ H ¹ α i 3

U 3 Φ P- H Φ (D [D φ l-i? Φ o rt Φ P> 3 φ 3 Φ H § Φ P)

1 • H P- H ι- (3 "P ⁾ C ι- <3 d tr CL 3 rt 3 Φ H <3

≤ α rt Hi rt rt O: 3 Φ rt Φ cn n? H φ ιQ HP ⁾ o P-

Φ o P> Hi Φ d tr 3 H Φ H O N tr O: Φ cn Φ Z. Φ cn H 3

P- p ^j Ö3 3 ≤ P> cn Φ N P- 3 rt p- £ Φ 3 H rt H Φ H rt r + P- 3 N 3 φ c Φ α 5 «P- P- a 3 Φ tr P Φ P > INI CL yQ P- α MH 3 ^• <P- H 3 Φ O dd φ rt P- Φ? O: 3 ^ Q Φ Φ

Φ ω d S rt n \ KH d 3 cn ^• υ φ 3 INI d tr Φ -3 Φ P- ■ - (t P- M Φ P & ⁾ " _^ PJ a 3 yQ ^ p ⁾ d • d H rt 3 P ⁾ P- Cn rt

Φ o O P> P- Φ H tr 3 (D α P ⁾ 3 P. vQ N Φ • H Φ O ?? Ud

3 3 ^ s: Φ 3 rt α H 3 HH 1 yQ 3 cn Φ HN rt 3 tr O Φ φ Hi Φ P- Φ rt tr ^ o Φ iQ rt P> P- Φ fτj m Φ P ⁾ 3 ιQ

3 o PJ 3 tr N Φ o cn Φ P- o 3 cn P_ Hi P- H Φ N> Hi cn Φ

Φ Ό 3 l-i P- tr O N rt σ P>: Hi h Φ Φ Hi rt P- P- Φ H Hi rt

0 £ rt P- ¹ tr 3 ^ Φ 3 φ Φ P- & a ⁾ P ⁾ ι-i Φ P- O P- σ φ P> cn rt 3 P- ≤ P- rt Φ 3 P- P- H 3 OH , ω> QH 3 rt P- 3 3 n

Hi 3 Φ P- rt Φ Φ 3 «rt rt 1 Φ Φ P ⁾ d P ⁾ P- φ Φ rt φ rt tr

P> P- HHH ι-J 3 l- ¹ P3 P- 1 & cn d 1 rt fj ¹ 3 Φ Φ

H "cn Φ 3 P- Φ CΛ α tr - _^ Φ 3? Rt P ⁾ Hi P>: 3 H tö 3 Φ L

O li O: P "Φ P- CL o (D Φ Φ α O Φ P> 3 _^ ? Α rt Φ ι_ι. D: P-

Φ 3 d vQ P- H 3 φ tr P P- H P> tr 3 3 Hi rt P> Φ li Φ P ¹ o P- Hi

0 P- 3 O c 0 ⁾ ns: cn tr 3 3 3 o P- P- Φ cn 3 3 α 3 Φ

• rt yQ P- tr 3 3 Φ Φ Ό O: 3 P- Hi H 3 3 Φ? R Hi

O ιQ α 0 ⁾ P- P- tr ^• Φ 3 P-? O N 3 cn P ⁾ d = α Ϊ

P> (tr 3 cn Φ 3 3 φ rt l_l. Cn Φ P ⁾ rt öd O d p- 3 tr Φ PJ d φ rt Φ NH α Φ Φ Φ φ PJ rt H rt HP>: dd ιQ rt φ 3 HH 3 o H t φ Φ 3 3 cn li d Φ P- tr rt ω 3 Φ p- d 3 tr α n P- NH ≤ ≤ Φ cn 3 O P- rt d = 3 ω 3 5ö

P- Φ rt d φ Φ tr φ S 3 H) P, 3 rt ι_ι. tr 1 Φ tr N o Q Φ α

P- φ Φ P, iQ 3 H Φ P- P ⁾ d: S tr H Φ P-? » P- φ Φ 3 ιQ d

P- H Φ 3 Φ rt cn cn H Φ tr d P- P ⁾ P- CL 3 o P. P- CL Φ H

Φ yQ P- rt H rt φ rt P- H cn rt d Φ φ rt tr rt 3 3 rt φ o

Φ ^> m 3 Φ Φ C: P- Φ 3 φ rt Φ cn H ω Φ P- P>: Φ H cn tr

Φ tr 3 Φ P- P- H- tr 3 α N N 3 Φ H ^ Q d H 3 tP 3 α o

P- Φ P> P- 3 Φ 3 (D • <Φ • ι- <Φ 3 m Φ 1 Φ P- ^• <s tr Φ vQ 3 3 P ¹ P- rt 3 rt cn X ⁴ P "P ¹ ≤ ιQ Φ P-> v p. ιQ m 3 J 3

Φ Φ P- 3 Φ Φ ω Φ P "3 Φ ω P- 3 H CL Φ P> φ rt

0 3 cn Φ H tr Ω 3 ^ 0 d φ ∑: P- H \ - ^j P ⁾ P- φ ιQ P- 3 rt P- cn rr O tr ¹ rt Φ 3 tr O ω 3 P- P> rt φ 3 3 3 3 H ¹ P- Φ Hi TJ

Tl tr 3 H Φ H ι-3 d φ σ Φ H Φ α N _^ o 3 cn N Φ H

P- M Φ φ ≤ P_ H Φ Φ 3 H Φ rt H) tr ¹ Φ P- ΪΛ> Φ O ^ <Φ

O P- H Φ Φ 3 P- P- α 3 Φ tr P- ⁾ 3 H Ό n Φ tr tr? yQ nfo> τj H 3 rt 1 φ P- Φ?: 3 "Φ O 3 g P ¹ Φ tr

Φ n M α • φ 3 ΪÖ tr P- Φ HHN φ P ⁾ φ ζ φ

P- P- Φ Φ H- rt φ o H 3 1 P- H. Φ Cn dd α -3 H d 3 (D: 3 rt o 3 3 ö Φ ^* tr Φ 3 α 3 υa HP ⁾ P> cn Hi 3 ^{^}

H α

P>: H ^ C iQ O 3 P- ÖÖ φ Φ P ¹ Φ o tP H l_ |. - • Φ tr rt P- öd H rt

_^ α φ 3 d 3 3 tr _^ 1 tr rt P "φ rt

P- Φ 1 d O Φ H 1 cn Φ • 1 Φ ^ 1 1 3 cn P> tr H 1 H 1 l

Arbitration with dynamic priority control is thus created by the present invention, which enables more flexible use of the bus resources.

Claims

claims

1. A method of managing bus access rights for multiple participants, comprising the following steps:

- allocation (1) of priorities for the access of the participants to the bus according to a predetermined pattern,

- Detection and evaluation (3) of the waiting cycles of the individual participants, which result from the actual stress on the bus, and

- Optimization of the priorities (4) for the access of the participants to the bus depending on the evaluation (3) of the waiting cycles.

2. The method according to claim 1, characterized in that the priorities are changed (4) in such a way that subscribers with long waiting cycles compared to other subscribers are assigned access rights with increased priority (1).

3. The method according to any one of claims 1 or 2, characterized in that the dynamic change (2) of the priorities is only temporary in the event that the waiting cycle of at least one participant exceeds a predetermined threshold, and otherwise a fixed priority assignment (1st ) according to a fixed order of priority.

4. The method according to any one of the preceding claims, characterized in that that the priorities are dynamically changed (2) in such a way that the waiting cycles of the different participants are substantially balanced.

5. A system for managing bus access rights for multiple participants, comprising:

- an arbiter (1) for assigning priorities for the access of the participants to the bus according to a predetermined pattern, - a priority control (2) for recording and evaluating the waiting cycles of the individual participants, which arise due to the actual stress on the bus, and For output to the arbiter (1) of changed priorities for the access of the participants to the bus depending on the evaluation of the waiting cycles.

6. System according to claim 5, characterized in that the priority control (2) outputs such changed priorities to the arbiter (1) that subscribers with long waiting cycles compared to other subscribers are assigned access rights with increased priority.

7. System according to one of claims 5 or 6, characterized in that the dynamic change of the priorities by the priority control (2) takes place only temporarily in the event that the waiting cycle of at least one participant exceeds a predetermined threshold, and otherwise the arbiter (1) executes a fixed priority.