Overhead-Aware Compositional Analysis of Real-Time Systems

Transcription

1 Overhead-Aware ompostonal Analyss of Real-Tme Systems Lnh T.X. Phan, Meng Xu, Jaewoo Lee, nsup Lee, Oleg Sokolsky PRESE enter Department of omputer and nformaton Scence Unversty of Pennsylvana

2 ompostonal Schedulng Analyss Root omponent 0 Large scale System Scheduler W 0 = {, } Open SA Lmted resource Real-tme embedded systems omponent-based desgn Modularty Reusablty Scalablty Portablty nterface RM nterface ntegrated from small systems Workload Leaf omponent Non-leaf omponent Workload W W SA: ompostonal Schedulng Analyss 3 4

3 Explct Deadlne Perodc Model EDP resource model Γ = ( Π, Θ, ) Π : Perod Θ : Executon tme : Deadlne Γ = ( Π0, Θ0, 0) 0 Γ = (0,6,6) W 0 Γ = ( Π, Θ, ) W ' Γ (,, ) = Π Θ ' W RM a) ompute EDP nterface of leaf component b) ompute EDP nterface of non-leaf component 3

4 ssues n Exstng SA,,..., 5 deadlne met 0 :(5,4.5,4.5) 0 W = {(5,4,5),(0,.0,0)} 0 n theory b) Scenaro n theory : (5,4,4) :(0,.0,.0) RM W = {(5,4,5)} W = {(500,,500 ),...} n practce,,..., 5 deadlne mssed a) Exstng SA s an nterrupt Servce Routne to release a task's job n each perod. 4 s c) Scenaro n practce nterface s Explct Deadlne Perodc (EDP) resource model here.

5 Strawman Soluton : nflatng WET Wth One Release rel s the tme t takes for an. 0 :(5,4.5,4.5) 0 W 0 = {(5,4,5),(0,.0,0)} e ' = e + rel : (5, 4.54,4.54 ) 0 0 W ={(5,4.0,5),(0,.04,0)} 0 rel = 0.0 : (5,4,4) :(0,.0,.0 ) RM W = {5,4,5} W = {(500,,500 ),...} : (5, RM 4.0,4.0) :(0,.04,. 04 ) W = {5, 4.0, 5 )} W = {500,.0, 500),...} a) Overhead-free SA b) SA after WET nflated wth one Unsafe! Schedulable n theory, not schedulable n practce. 5

6 Strawman Soluton : nflatng WET Wth Total Release s? n s the number of tasks n the whole system. 0 :(5,4.5,4.5) 0 e ' = e + n j = p p j rel : (5, 6.63,5) 0 0 W 0 = {(5,4,5),(0,.0,0)} W 0 = {(5,5,5), (0,4.08,0)} rel = 0.0 : (5,4,4) :(0,.0,.0 ) RM a) Overhead-free SA W = {5,4,5} W = {(500,,500 ),...} : (5, RM 5,5 ) : (0, 4.08,4. 08 ) W = {5, 5.0, 5 )} W ={500, 4, 500),...} b) SA after WET nflated wth one mpossble to get n n a compostonal settng! Because the task nformaton wthn one component s hdden from another component. 6

7 ontrbutons Overhead-aware schedulablty analyss ntroduce an overhead-aware schedulablty test for one component Overhead-aware nterface Defne a new nterface to ncorporate platform overheads Overhead-aware nterface computaton Propose a method to compute each component's nterface Evaluaton on an expermental platform llustrate the applcablty and benefts of our overheadaware analyss 7

8 Overheads sch cxs RPD ( tch, ptck ) Schedule overhead ontext swtch overhead ache related preempton delay of task Tck overhead nflatable overheads rel Release overhead Non-nflatable overheads Focus on non-nflatable overhead accountng n compostonal schedulng analyss. Apply exstng approach for nflatable overheads. 8

9 nflatable Overhead Accountng a) Release event overheads relev preev e ' = p = = tck sch sch e e + e ' = p tck + + tck relev cxs b) Preempton event overheads cxs p + tck tck preev + c) Tck event overheads nflated WET RPD p tck () () (3) (4) [] cpu j cpu rel (a) Release event related overhead sch sch cxs RPD e (b) Preempton event related overhead c) Tck overhead cxs e [] B. B. Brandenburg. Schedulng and Lockng n Multprocessor Real-Tme Operatng Systems. PhD thess, The Unversty of North arolna at hapel Hll, 0. 9

10 nflatable Overhead-Aware Analyss =, A : omponent has task set, scheduled under schedulng polcy A. A component =, A s schedulable by a resource R n the presence of nflatable overheads f ' ts nflated workload s schedulable by R under A n the absence of overheads. Proof s n the paper. 0

11 Overheads sch cxs RPD ( tch, ptck ) Schedule overhead ontext swtch overhead ache related preempton delay of task Tck overhead nflatable overheads rel Release overhead Non-nflatable overheads

12 Non-nflatable Overhead Accountng hallenge Release execute ASAP when t s nvoked Release cannot be delayed by tasks or scheduled Release delay can accumulate,...,, 5 deadlne mssed s Release property

13 Non-nflatable Overhead Accountng Modelng release s n a compostonal manner Release s modeled n a hgher prorty ntracomponent Workload modeled n a lower prorty component Scheduled by FP Request bound functon of release same perod of ts task rel executon tme no deadlne 3 =, = rbf = rbf where rbf = t p rel The nterface for release s s ()

14 Non-nflatable Overhead-Aware Analyss A component =, A s schedulable by a resource R n the presence of ntra-component release s overhead f =, A s schedulable by a resource R' n the absence of overheads, where R' s the remanng resource after servces release s overhead frst. R sbf R' = sbf rem R, def = max{ sbf 0 t' t R ( t') rbf ( t')} () Proof s n the paper. 4

15 Non-nflatable Overhead-Aware Analyss Schedulable Example =, = {(0,,0),(0,,0),(0,,0),(0,5,0)} rel = 0. 0 rbf t t t t = 0.0( ) t t = 0.04( + ) 0 0 () 5

16 Non-nflatable Overhead-Aware Analyss Unschedulable Example =, =,,..., } { 0 t 5 t 500 rel = 0.0 rbf = 0.0( + 00 ) = (5,4,5) =... 0 = (500,,500) 6

17 ontrbutons Overhead-aware schedulablty analyss ntroduce an overhead-aware schedulablty test for one component Overhead-aware nterface Defne a new nterface to ncorporate platform overheads Overhead-aware nterface computaton ntroduce a method to compute each component's nterface Evaluaton on an expermental platform llustrate the applcablty and benefts of our overheadaware analyss 7

18 Overhead-Aware SA: nterface Representaton nterface: =, = rbf = rbf where Example: Workload nterface; Resource model for workload wth nflatable overheads nterface; Resource model for release s overhead rbf =, = t p rel 8 =, nterface representaton '= {(0,,0),(0,,0),(0,,0),(0,5,0)} rel = 0. 0 = ( 0,6,6), rbf rbf = 0.0( ) = 0.04( + ) t 0 () t 0 t 0 t 0 t 0 t 0

19 an we use exstng nterface models to specfy? 9

20 an we use exstng nterface models for Suppose Γ = ( Π, Θ, ) Example: uses EDP model FP? : (,0.906,) =, = {,,..., 5} = (5,4,5) = = (500,,500 ) 5 = rel = 0.0 s schedulable n analyss But not schedulable n practce! So cannot use EDP model! 0,,..., s (,0.006,) :(5,4.5,5 ) 5 : Release = {,..., 5} a) Scenaro n analyss deadlne mssed b) Scenaro n practce

21 Reason why exstng nterfaces do not work Release s property Execute ASAP when nvoked Not delayed by tasks Resource model for Amortze s requrement to each perod s are "scheduled" Worst-case release delay no longer exsts amortzaton problem: s amortzed to each perod.,,,..., s,..., s 5 5 deadlne mssed a) Scenaro n practce deadlne met b) Scenaro n analyss

22 Overhead-Aware SA: nterface Representaton nterface: =, =, = rbf = rbf where Workload nterface: resource model for workload wth nflatable overheads nterface: resource model for release nterference rbf t = p rel nterface representaton

23 ontrbutons Overhead-aware schedulablty analyss ntroduce an overhead-aware schedulablty test for one component Overhead-aware nterface Defne a new nterface to ncorporate platform overheads Overhead-aware nterface computaton ntroduce a method to compute each component's nterface Evaluaton on an expermental platform llustrate the applcablty and benefts of our overheadaware analyss 3

24 Overhead-Aware nterface omputaton ompute leaf components' nterface ompute non-leaf components' nterface Example to llustrate W 0 0 W = { = (00,0,00), = (00,0,00)} W = { 3 = (00,0,00), 4 = (00,50,00)} W W RM rel = 0.0 sch = 0. 0 cxs = 0.0 RPD 0. 0 )= tck (, p ) = (0.0, tck Overhead value 4

25 ompute Leaf omponent's nterface Step /4: ompute the nflated WET e nflate nflatable overheads e + e ' = p relev tck + tck preev p tck ' e ' e W W = (00,0,00) = (00,0,00 ) = (00,0,00) 3 4 = (00,50,00) ' = ' = 3 ' = 4 ' = (00,,00) (00,,00) (00,,00) (00,5,00) W ' W ' 5

26 ompute Leaf omponent's nterface Step /4: Generate a bandwdth-optmal EDP nterface = Γ ' = ( Π, Θ, ) as the workload nterface for the nflated workload 0 W ' =, = (0,3.,3. ) W 0 W ' =, = (0,3.,3.) =, =, W ' ' W RM 6

27 ompute Leaf omponent's nterface Step 3/4: ompute the = rbf (t) that bounds the ntra-component release nterference overheads = rbf = rbf, wth rbf t = p rel ' = ' = (00,,00) (00,,00) rel =0.0 = (00,0.0) = (00,0.0) = rbf = t ' = 4 ' = (00,,00) (00,5,00) 3 = (00,0.0) 4 = (00,0.0) = rbf = t

28 ompute Leaf omponent's nterface Step 4/4: The overhead-aware nterface of =, Γ ' = = rbf, where and s 0 = W ' W 0, =, ' W RM =, =, = (0,3.,3.) = rbf = = (0,3.,3.) = rbf t t =

29 Overhead-Aware nterface omputaton ompute leaf components' nterface ompute non-leaf components' nterface = 0 0, 0 0 = (0,3.,3.) W 0 =, = rbf = t =, = W ', ' W RM =, = (0,3.,3.) = rbf = t

30 ompute Non-leaf omponents' nterface Suppose = W = {,..., n}, A where =, and =, omposton =... n n = = = 0 0, W nterface = (0,3.,3.) = (0,3.,3.) nterface Task T = (0,3.,0) T = (0,3.,0) =, =, W ' ' W RM 0 = (0,6.3,6.3) 30

31 ompute Non-leaf omponents' nterface Suppose = W = {,..., n}, A where =, and =, omposton =... n n = = = t, 0 = rbf ' = W 0 t = rbf ' = =, =, W ' ' W RM 0 t t = rbf ' = ( + )

32 ompute Non-leaf omponents' nterface Suppose = W = {,..., n}, A where =, and =, omposton =... n n = = =, W = (0,6.3,6.3) 0 t t = rbf ' = ( + ) =, =, W ' ' W RM 3

33 ontrbutons Overhead-aware schedulablty analyss ntroduce an overhead-aware schedulablty test for one component Overhead-aware nterface Defne a new nterface to ncorporate platform overheads Overhead-aware nterface computaton ntroduce a method to compute each component's nterface Evaluaton on an expermental platform llustrate the applcablty and benefts of our overheadaware analyss Proof of correctness of the overhead-aware compostonal analyss s n the paper. 33

34 Evaluaton on an Expermental Platform EDP approach Not consder any platform overheads Baselne approach nflatng each task's WET by all types of overheads, ncludng the release s overheads e + e ' = relev p tck + preev tck + e rel p tck where relev sch cxs preev sch cxs RPD = +, = + +, e rel = j p p j rel and 34

35 Evaluaton Setup Task's perod Task's utlzaton # of Guest Doman Hardware Software unformly n [0ms, 00ms] unform unformly n [0.0%,0.5%] lght bmodal medum bmodal heavy bmodal Doman perod Task 8/9 n [0.0%,0.5%] and /9 n [0.5,0%] 6/9 n [0.0%,0.5%] and 3/9 n [0.5,0%] 4/9 n [0.0%,0.5%] and 5/9 n [0.5,0%] Doman 64ms Platform Schedulng Dell Optplex-980 quad-core processor RT-Xen 0.3 DM Doman 0 Pn to core0 Doman & Pn to core Overhead Value p rel sch cxs RPD tck tck = 3.77 µ s = = µ s = µ s = 39. µ s 4.77 µ s = ms. Overhead value s measured by feather trace on LTMUS on the same hardware. 35

36 Safe and Detect More Schedulable Task Set Fg. Fracton of schedulable task sets vs. workload utlzaton 36

37 Save Resource Bandwdth Fg. Resource bandwdth requrement 37

38 Save Resource Bandwdth Under Dfferent Load Fg. 4 Resource bandwdth requrement under dfferent load stuatons 38

39 oncluson ontrbutons: Overhead-aware schedulablty analyss for one component Overhead-aware nterface Overhead-aware nterface computaton Evaluaton on an expermental platform Future work consder practcal component overhead overhead-aware SA on multcore platform 39

40 Thank you! 40