Efficient Implementation of Concurrent Programming Languages

Transcription

1 Uppsl Dissettions fom the Fculty of Science nd Technology 43 ERIK STENMAN Efficient Implementtion of Concuent Pogmmg Lnguges ACTA UNIVERSITATIS UPSALIENSIS UPPSALA 2002

2 ACTA UNIVERSITATIS UPSALIENSIS Uppsl Dissettions fom the Fculty of Science nd Technology 43

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4 Eik Stenmn Efficient Implementtion of Concuent Pogmmg Lnguges

5 Dissettion fo the Degee of Docto of Philosophy Compute Science pesented t Uppsl Univesity Abstct Stenmn, E. 2002: Efficient Implementtion of Concuent Pogmmg Lnguges, Act Univesittis Upsliensis. Uppsl dissettions fom the Fculty of Science nd Technology pp. Uppsl. ISBN This thesis poposes nd expeimentlly evlutes techniques fo efficient implementtion of lnguges designed fo high vilbility concuent systems. This expeimentl evlution hs been done while developg the High Pefomnce Elng (HiPE) system, ntive code compile fo SPARC nd x86. The two m gols of the HiPE system e to povide efficient execution of Elng pogms, nd to povide esech vehicle fo evlutg implementtion techniques fo concuent functionl pogmmg lnguges. The focus of the thesis is the evlution of two techniques tht enble tepocess optimiztion though dynmic compiltion. The fist technique is fst egiste llocto clled le scn, nd the second is memoy chitectue whee pocesses she memoy. The m contibutions of the thesis e: An evlution of le scn egiste lloction diffeent lnguge settg. In ddition the pefomnce of le scn on the egiste poo x86 chitectue is evluted fo the fist time. A desciption of thee diffeent hep chitectues (pivte heps, shed hep, nd hybid of the two), with systemtic vestigtion of implementtion spects nd n extensive discussion on the ssocited pefomnce tde-offs of the hep chitectues. The desciption is ccompnied by n expeimentl evlution of the pivte vs. the shed hep settg. A novel ppoch to optimizg concuent pogm, by megg code fom sende with code fom eceive, is pesented togethe with othe methods fo educg the ovehed of context switchg. A desciption of the implementtion spects of complete nd obust ntive code Elng system, which mkes it possible to test compile optimiztions on el wold pogms. Eik Stenmn, Deptment of Infomtion Technology, Uppsl Univesity, Box 337, SE Uppsl, Sweden. c Eik Stenmn 2002 ISSN ISBN Pted Sweden by Elndes Gotb, Stockholm 2002.

6 To my pents nd my wife.

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8 Acknowledgments The dys e ll empty nd the nights e Unel. cookie Fist nd foemost I would like to thnk my supeviso Konstntos (Kostis) Sgons. Without his guidnce, dvice, nd will to help this thesis would neve hve been completed, o even stted. I should lso note tht this esech hs been suppoted pt by the ASTEC (Advnced Softwe Technology) competence cente with mtchg funds by Eicsson Development. A big compile poject like the HiPE compile is tem effot, nd I m gteful to sevel people fo the completion of the HiPE compile. Fist of ll I m gteful to my oigl supeviso Håkn Milloth fo lettg me do Mste s thesis on compiltion of Elng, nd to Thoms Ldgen fo tkg ove the poject when Håkn left. Much of the itil vesion of the HiPE system is due to my Mste s thesis ptne Chiste Jonsson. In the JERICO compile he wote the bck-end nd untime system suppot. As we stted on the HiPE compile we switched oles nd he wote the font-end, the gph colog egiste llocto, nd othe optimiztions. Chiste ws get souce of spition, nd it felt secue to hve such knowledgeble ptne. Without him by my side I would pobbly neve hve undetken such n mbitious poject s the HiPE system. Mikel Pettesson, who took ove the poject when Thoms Ldgen left, is lso vey knowledgeble compile hcke, nd he lwys hd n nswe nd could suggest solution to ny implementtion poblem I encounteed. He is esponsible fo most of the untime system suppot nd he is the m designe of the x86 bck-end. Sevel othes hve lso hcked on nd ound the HiPE compile: Kostis Sgons wote the BEAM disssemble, nd the BEAM to Icode tnsltion. Richd Clsson wote help libies such s pop-lists nd i

9 ii woked on the tefce to the ody Elng compile. Sven-Olof Nystöm wote the genelized blnced tee implementtion which is the coe of mny dt stuctues the HiPE compile. Thee hve lso been mny Mste s students nd students the Compiles-2 couse hckg on the system, fo exmple: Andes Wll, Thoild Selén, Ingem Åbeg who wote the fist vesion of the colescg egiste llocto. Ulf Mgnusson who woked on the x86 bck-end. Chistoffe Vikstöm, Dniel Deogun, nd Jespe Bengtsson who implemented the SSA convesion Icode. Pe Gustfsson who implemented fst suppot fo bies. Tobis Ldhl who wote the ntive suppot fo flotg pot opetions. Lst, but not lest, I would like to thnk Jespe Wilhelmsson who implemented most of the untime suppot fo the shed hep system. We hve lso hd much vluble help fom the Elng/OTP tem t Eicsson, nd I would especilly like to thnk Bjön Gustfsson fo his ptience with ll my questions bout the system, nd fo ll the effot he put to mkg the Elng/OTP system suppot HiPE. I hve lso hd lot of help witg this thesis, nd the ppes it is bsed on, nd I would g like to thnk Kostis Sgons fo ll the help with the witg nd fo helpg me see wht is impotnt. I would lso like to thnk Sven-Olof Nystöm fo mny vluble comments on the thesis. Sce much of this thesis is tken moe o less stight fom peviously published ppes some of the wodgs might be those of my couthos: Kostis Sgons, Mikel Pettesson, Sven-Olof Nystöm, Jespe Wilhelmsson, nd Thoms Ldgen. I lso got vluble comments on my thesis fom my opponent Simon Peyton-Jones, nd lguistic help fom my wife Cecili Stenmn. My fiends t the deptment hs mde my time s Ph.D student enjoyble. In the begng Pe Mildne, Chiste Jonsson, Gustf Gffe Nese, Gege Ottosson, nd dug the yes Jkob Engblom, nd Jespe Wilhelmsson. Most vluble thoughout this whole time hs been my gowg fiendship with Richd Clsson. He hs been get help, both s esech collegue to discuss new (nd old) ides with, nd s fun fiend to emisce bout vtge home computes 1 ove bee. My time Uppsl hs been mde fun by Bikln, the Gmes- Dom gng who iegully joed me ll night LAN-pties, nd ll my othe fiends. I m lso gteful to hve found my closest fiend, 1 Fo us vtge is the begng of the eighties.

10 iii Fedik Stöm hee Uppsl. He hs spied nd encouged me sce the fist dy of ou compute science studies. My fmily hs lwys been vey impotnt to me. Fo lwys believg me, nd fo buyg me my fist thee computes, enblg me to tke this pth life, I m etenlly gteful to my pents. Wods e not enough to expess my gtitude towd my eve lovg nd suppotg wife who helped me though ll the though times of my Ph.D. studies. Hvg to give up my lst nme ws smll pice to py to get he s my wife. Thnk you, Cill!

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12 Foewod The tools we use hve pofound (nd devious!) fluence on ou thkg hbits, nd, theefoe, on ou thkg bilities. Edsge Dijkst At the ge of 17 I ws fotunte enough to spend one ye s n exchnge student the USA. This ws deed n eductionl ye, nd believe it o not, one of the most memoble expeiences ws elted to the ctul pupose of the tip: the leng of lnguge. When I ived the Sttes my gsp of the English lnguge left much to desie, nd my vocbuly ws quite limited, but I got by. As the dys went by the constnt witg, edg, spekg, nd listeng to English flly foced me to stt thkg English. At fist I ws delighted, this ws get, I could tect with my envionment much fste when I no longe hd to constntly tnslte evey sentence to Swedish, thk up esponse nd then tnslte tht bck to English. The joy ws not long lstg though; I soon found tht I hd become less witted. My limited English vocbuly mde it impossible to thk cet thoughts; I simply lcked the wods. This tught me n impotnt lesson bout the powe of lnguge: If you lnguge (o you gsp of it) is not up to the tsk, you put you telligence nd cetivity t isk. I hve cied this sight with me eve sce, even to the wold of pogmmg lnguges. Hence, I hve lwys stived to fd lnguges tht e poweful enough to esily expess the concepts t hnd. To me, Elng with its built suppot fo concuency is such lnguge. In the bsence of scientific study of the poductivity diffeent lnguges I hope tht my pesonl motivtion to the impotnce of Elng is enough to ouse you teest the efficient implementtion of Elng nd othe simil lnguges. v

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14 Pio Publictions This thesis is to lge extent bsed on the followg ppes. 2 I. E. Johnsson, S.-O. Nystöm. Pofile-guided optimiztion coss pocess boundies. Poceedgs of ACM SIGPLAN Wokshop on Dynmic nd Adptive Compiltion, II. E. Johnsson, M. Pettesson nd K. Sgons. A High Pefomnce Elng System. Poceedgs of the 2nd ACM SIGPLAN Intentionl Confeence on Pciples nd Pctice of Decltive Pogmmg, III. E. Johnsson nd K. Sgons. Le Scn Registe Alloction High-Pefomnce Elng Compile. Poceedgs of the 4th Intentionl Symposium, Pcticl Aspects of Decltive Lnguges, IV. E. Johnsson, K. Sgons, nd J. Wilhelmsson. Hep Achitectues fo Concuent Lnguges usg Messge Pssg. Poceedgs of the ACM SIGPLAN Intentionl Symposium on Memoy Mngement, V. M. Pettesson, K. Sgons, nd E. Johnsson. The HiPE/x86 Elng Compile: System Desciption nd Pefomnce Evlution. Sixth Intentionl Symposium on Functionl nd Logic Pogmmg, VI. E. Stenmn nd K. Sgons. On Reducg Intepocess Communiction Ovehed Concuent Pogms. Poceedgs of ACM SIGPLAN Elng Wokshop, VII. E. Johnsson, M. Pettesson, K. Sgons, nd T. Ldgen. The Development of the HiPE System: Design nd Expeience Repot. Accepted, will ppe the Spge Intentionl Jounl on Softwe Tools fo Technology Tnsfe. VIII. E. Stenmn nd K. Sgons. Expeimentl evlution nd impovements to le scn egiste lloction. Submitted fo publiction. 2 Note tht the utho hs chnged nme fom Eik Johnsson to Eik Stenmn. vii

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16 Contents I Pefce 1 1 Intoduction Poblem sttement Contibutions of this thesis Thesis oveview Bckgound Elng Concuency Elng Memoy mngement Elng nd othe concuent lnguges Uses of Elng Gols of HiPE A bief histoy of HiPE JERICO: The fist pototype Compile Cllg conventions nd stck fmes Bckptchg Pefomnce of the JERICO compile The HiPE system befoe Open Souce Elng Open souce HiPE HiPE 1.0/OTP-R HiPE 2.0/OTP-R Some specil HiPE fetues II Implementtion 29 3 The compile fstuctue Phses the compile ix

17 x CONTENTS To BEAM code BEAM to Icode Icode to RTL Symbolic SPARC Symbolic IA Registe lloction Fme mngement Leizg the code Assemblg the code Intefce issues Tilclls Exception hndlg Stck desciptos Gbge collection nd genetionl stck scnng Mode switchg Built- functions Pocess switchg Code lodg Ptten mtchg implementtion Registe lloction Globl egiste lloction Gph colog egiste lloction Iteted egiste colescg Le scn egiste lloction Implemented egiste lloctos HiPE Gph colog egiste llocto Iteted egiste colescg llocto Le scn egiste llocto A nïve egiste llocto The SPARC bck-end The x86 bck-end Tweks fo le scn on the x Relted wok Discussion Hep chitectues An Achitectue with Pivte Heps Pocess communiction Gbge collection Pos nd cons An Achitectue with Shed Hep

18 CONTENTS xi Pocess communiction Gbge collection Pos nd cons Optimiztions Poposg A Hybid Achitectue Alloction sttegy Pocess communiction Gbge collection Pos nd cons Pefomnce of pototype Relted Wok Discussion Pocess optimiztion Reschedulg Send Diect Disptch Intepocess Inlg The tnsfomtion Futhe considetions Retun messges Expeiencesfompototype Potentil gs Relted Wok III Evlution 91 7 Pefomnce of HiPE Elng vs. othe functionl lnguges Compison of Elng implementtions Compison of ntive vs. emulted code Discussion Pefomnce of egiste lloctos Benchmks Compiltion times Speed of Execution Spills on SPARC Spills on x A deepe look on le scn Impctofstuctionodeg Impct of pefomg liveness nlysis

19 xii CONTENTS 9.3 Impct of spillg heuistics Lifetime holes nd live nge splittg A compison of hep chitectues The benchmks nd the settg A compison of pivte hep vs. shed hep chitectue Time pefomnce Stop times Spce pefomnce Summy IV Conclusion Conclusion Summy of contibutions Discussion Futue Resech Refeences 141

20 List of Figues 2.1 A ntive stck fme JERICO Bckptchg when code fo the functions g the cllch f g h is eloded. The new code clls q (not shown) sted of h Stuctue of HiPE-enbled Elng/OTP system Recusive clls (f g) nd tilclls (g til h) The Icode CFG s fo the functions g nd f fom Pogm 3.1. Note tht the cll to g fom f is potected by nexceptionhndle(bsicblock3) The cll stck fo fo the functions g/m the cll ch f/l g/m h/n A stck descipto fo cll (on SPARC) to h/0 fom g/17. Note tht 16 of the guments to g/17 e pssed egistes nd tht 1 locl vible is live dug the cll to h/ Mode-switch fmes ceted cll f g h Code bckptchg done by HiPE lke Contol-flow gph nd two of its possible leiztion Memoy chitectue with pivte heps Messge pssg pivte hep system Memoy chitectue with shed hep Messge pssg shed hep system A hybid memoy chitectue Messgepssghybidchitectue Pocess megg Compiltion times on SPARC Compiltion times, with SSA convesion, on SPARC xiii

21 xiv LIST OF FIGURES 8.3 Compiltion times on x Compiltion times, with SSA convesion, on x Execution times on SPARC Execution times, with SSA convesion, on SPARC Execution times on x Execution times, with SSA convesion, on x Estone nkg on SPARC nd x Estone nkg on SPARC nd x86 with SSA convesion A simple contol flow gph A contol-flow gph nd its odegs Nomlized times fo the pocs benchmk Nomlized execution times Mx gbge collection stop times (ms)

22 List of Tbles 4.1 Use of SPARC egistes HiPE Use of x86 egistes HiPE Pefomnce of functionl lnguges on thee ecusive pogms nd one concuent. Execution times seconds Times ( seconds) fo sequentil benchmks diffeent Elng implementtions Speedup of diffeent Elng implementtions comped to JAM Times ( seconds) nd speedup ove JAM fo concuent benchmks diffeent Elng implementtions Times ( seconds) nd speedup ove JAM fo lge benchmks diffeent Elng implementtions Speedup of HiPE-1.0 ove BEAM R Desciptionofbenchmkpogms Sizes of benchmk pogms Numbe of spilled tempoies nd SPARC stuctions fte lloction Numbe of spilled tempoies nd SPARC stuctions fte lloction (with SSA) Numbe of spilled tempoies nd x86 stuctions fte lloction Numbe of spilled tempoies nd x86 stuctions fte lloction (with SSA) Numbe of spilled tempoies usg diffeent bsic block odegs Numbe of spilled tempoies usg diffeent bsic block odegs(withssa) Impct of spillg heuistics xv

23 xvi LIST OF TABLES 10.1 Numbe of pocesses nd messges Hepsizeslloctedndused(1,000wods)...131

24 Pt I Pefce 1

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26 Chpte 1 Intoduction Obviously, the med lnguge hs enomous momentum. I m not poposg tht you cn fight this poweful foce. Wht I m poposg is exctly the opposite: tht, like pctitione of Aikido, you cn use it gst you opponents. Pul Ghm This thesis poposes nd expeimentlly evlutes techniques fo efficient implementtion of lnguges designed fo high vilbility concuent systems. A concuent system is system tht is designed s collection of dependent pocesses. Fom the view of the designe these pocesses e pefomg thei tsks simultneously, but elity thei execution might be televed on sgle pocesso. We distguish between concuent pocesses, i.e., pocesses tht conceptully e executg simultneously, nd pllel pocesses, i.e., pocesses tht elity e executg simultneously on, e.g., multipocesso mche. Mny systems lend themselves ntully to concuent implementtion, notbly tective systems which extenl events dictte the execution ode, nd distibuted systems whee tsks e executed pllel on diffeent nodes. The concept of pocesses is lso impotnt s n bstction. A pocess encpsultes stte ntul wy; this espect pocesses esemble objects n object-oiented lnguge. It is hence not supisg tht ecent yes, concuency s fom of bstction hs become cesgly popul, nd mny moden pogmmg lnguges (such s Occm [62], CML [78], Oz [90], Elng [10], Jv [39], nd C#) come with some fom of built- suppot fo concuent pocesses (o theds). Mny of these lnguges belong to the ctegoy tht we will cll concuent functionl pogmmg lnguges (CFPL). A CFPL is functionl pogmmg lnguge with built- suppot fo concuency. One ppliction e, with equiements tht lend themselves ntully to the use of concuent functionl pogmmg lnguge, is

27 4 CHAPTER 1. INTRODUCTION tht of the tele-communictions (telecom) dusty. Most moden systems povided by the telecom dusty, such s telephone exchnges, Intenet seves, nd outes, hve vey high vilbility equiements. Usully, these systems equie five nes vilbility, tht is % uptime. O put nothe wy: less thn five mutes downtime pe ye, cludg ll plnned stops fo mtennce nd updtes. Anothe chcteistic of these systems is tht it is often ntul to model them s lge set of concuent tsks o subsystems. The competitiveness of the telecom dusty lso demnds shot development times. Sce lge pts of these systems e implemented softwe, the telecom dusty hs need fo softwe development envionments tht cn suppot the fst development of highly concuent, fult-tolent systems. Anothe equiement of telecom systems is tht they e supposed to un vitully foeve. This is f fom the kd of web-pplictions tht one wites e.g., Jv, which executes fo few mutes o hous t most. It is lso f fom usul use level pogms such s one would build with, e.g., Micosoft Visul studio nd un unde Wdows. Nobody expects these systems to execute contuously fo yes. The lifetime of bckbone telephone exchnge, on the othe hnd, hs these kds of equiements. Few softwe development tools clim to cte fo such exteme equiements. But the Open Telecom Pltfom (OTP) povided by Eicsson is such tool nd it hs poved itself sevel telecom pojects dug the lst ten yes. The coe technology of OTP is the concuent functionl pogmmg lnguge Elng. It is impotnt tht the untime pefomnce of pplictions developed Elng is s good s possible. Fste execution cn diectly be tuned to the bility to hndle moe uses, clls, connections, equests, etc, o the bility to hndle the sme numbe of uses with chepe hdwe. Also, if the pefomnce of the Elng system is too low o cet lnguge fetues give suboptiml pefomnce, the develope will be tempted to use unntul bstctions ode to chieve cceptble pefomnce. Theefoe, we believe tht it is impotnt to fd genelly pplicble implementtion techniques fo concuent functionl pogmmg lnguges tht ensue high untime pefomnce. To tckle this poblem we hve stted the HiPE (High Pefomnce Elng) poject. The m contibution of the HiPE poject is the HiPE system with ntive code Elng compile fo SPARC nd x86. Ou m gol with the HiPE system is to povide the most efficient execution of Elng pogms. Anothe im of the HiPE system is to povide esech

28 1.1. PROBLEM STATEMENT 5 vehicle tht cn be used to evlute implementtion techniques fo concuent functionl pogmmg lnguges. We hve tied to mke well stuctued, open, nd modul system which llows pogmmg lnguge implemento to plug nd ply pts of the system, ode to evlute diffeent implementtions of one component while keepg the est of the system unchnged. We believe tht the ntue of distibuted tective systems mkes the use of sttic nlysis sub-optiml. These systems hve huge code bse nd e developed modul units mkg whole pogm sttic nlysis poblemtic. As mentioned, these systems hve to cte fo code updtes unng system, which complictes the implementtion of sttic nlysis nd optimiztion scheme. And flly, these systems e vey dynmic ntue, mkg one-time sttic nlysis impecise. Insted of usg sttic nlyses we suggest tht some optimiztion of such systems should be pofile-guided nd pefomed dynmiclly (done t untime). With the HiPE system we hope to cete untime system fo Elng tht hs the bility to econfigue nd e-optimize itself unng system without focg the system to go offle. Fo exmple, fst compile, which spends little time on egiste lloction, cn be used just--time compiles nd fo systems with dynmic ecompiltion. This opens up new oppotunities fo optimiztion nd cn ultimtely led to fste execution comped to system tht compiles the pogm only once, even if this compile poduces n optiml egiste lloction. To chieve the most efficient execution of Elng pogms we need to fd out which pts of the Elng system need to be impoved nd how the execution of Elng pogms cn be optimized. Then we need to fd techniques to implement these optimiztions, nd flly we need to tune the implementtion of these techniques so tht they cn be pplied t untime without distubg the execution of the ppliction. In this thesis sevel techniques to chieve efficient execution of concuent functionl pogmmg lnguges e studied. Even though the focus of the thesis is on the pplicbility of these techniques to Elng, we stess tht they e pplicble to othe pogmmg lnguges nd systems s well. 1.1 PROBLEM STATEMENT As stted peviously, the gol of this thesis is to fd nd evlute efficient implementtion techniques fo CFPLs though pofile-guided dynmic ecompiltion. Dynmic ecompiltion equies fst compile, so we hve studied egiste lloction sce this pt of the compile often is compiltion time bottleneck. In ode to mke te-pocess

29 6 CHAPTER 1. INTRODUCTION communiction moe efficient we would like to hve ccess to shed memoy, nd theefoe we study the impct of shed hep chitectues. With fst compile nd shed memoy new pocess optimiztion techniques cn be developed. Hence, this thesis mly focuses on thee sub-poblems, 1) egiste lloction, 2) hep chitectues suppotg communiction though messge pssg, nd 3) pocess optimiztion, but it lso pesents some genel sights on the development of pogmmg lnguge systems. Let us look t these thee poblems little moe detil. Registe lloction The fstest memoy loctions moden computes e the egistes. Unfotuntely the numbe of egistes is limited, hence it is impotnt to use them s efficiently s possible. The egiste llocto is the pt of compile esponsible fo fdg n effective use of egistes. This is one of the hdest nd most centl poblems to compile nd extensive esech hs been conducted this e. We study thee diffeent egiste lloctos nd compe thei pefomnce to ech othe nd gst nïve llocto, which keeps ll tempoies on the stck. Two of the lloctos e vts of the lloction technique we suspect is the most commonly used technique moden compiles, nmely gph colog. The thid, eltively new technique, clled le scn, is designed with fst compiltion times md, nd hence is well suited fo just--time compiltion. A somewht supisg esult of this compison is tht even though the impct on pefomnce of egiste lloction comped to the nïve ppoch is significnt, when compg the thee lloctos with ech othe thei pefomnces e simil. We extend pevious esech done on le scn egiste lloction by pplyg it to new poblem e, nmely just--time compiltion of functionl pogmmg lnguges. We show tht le scn pefoms well even though the undelyg implementtion equies eltively lge numbe of pecoloed egistes. We lso povide the fist ppliction of le scn to egiste poo chitectue such s x86, nd show tht it pefoms esonbly well tht context too. Flly, we lso evlute sevel vts to the lgoithm to fd the most efficient implementtion. Hep chitectues A key issue the design of concuent lnguge implementtion is the memoy chitectue of the untime system. Thee exist mny diffeent wys of stuctug the chitectue of the untime system, ech hvg its pos nd cons.

30 1.2. CONTRIBUTIONS OF THIS THESIS 7 We pesent thee memoy chitectues fo high-level pogmmg lnguges tht implement concuency though messge pssg. 1 The thee chitectues e 1) pivte hep system, which ech pocess hs its own pivte memoy, 2) shed hep system which ll pocesses she the memoy one common hep, nd 3) hybid system with pivte heps fo pivte dt nd shed hep fo messges. We systemticlly vestigte spects tht fluence the choice between them, nd extensively discuss the ssocited pefomnce tdeoffs. Moeove, n implementtion settg whee the est of the untime system is unchnged, we pesent detiled expeimentl compison between two of these chitectues both on lge highly concuent pogms nd on synthetic benchmks. Pocess optimiztion The use of concuency often hides pts of the dt flow fom the compile. This mkes mny of the common compile optimiztions of tody hd o even impossible the cse of tepocess communiction, the sme wy s the use of pocedues limits the optimiztions compiles tht does not employ te-pocedul optimiztions. As stted, the dynmic ntue of the pplictions we e vestigtg mkes sttic nlysis hd nd impecise. Hence, we popose the use of pofilg to deteme the te-pocess dt flow n ppliction. The collected fomtion cn then be used to optimize the code by fo exmple complete o ptil pocess megg. We pesent method fo ptil pocess megg whee the code sendg messge is meged with the code tht will eceive the messge. 1.2 CONTRIBUTIONS OF THIS THESIS To summize the contibutions of this thesis by e, they e: Registe lloction A thoough evlution of le scn egiste lloction settg diffeent fom the impetive one tht it hs been pplied to peviously. A compison of le scn with thee othe egiste lloctos. The fist evlution of the pefomnce of le scn on the egiste poo x86 chitectue. 1 Even lnguges, such s Jv, tht implement pocess communictions though shed stuctues cn use these thee chitectues, but the tde-offs fo such lnguge e diffeent thn fo lnguge tht uses messge pssg.

31 8 CHAPTER 1. INTRODUCTION An evlution of the effect of options to the bsic lgoithm. Hep chitectues A desciption of thee diffeent hep chitectues (pivte heps, shed heps, nd hybid of the two) with systemtic vestigtion of implementtion spects. An extensive discussion on the ssocited pefomnce tdeoffs of ech of the thee hep chitectues. An expeimentl evlution of the two exteme chitectues on both el wold pogms nd tificil benchmks, pefomed n othewise unchnged untime system. Pocess optimiztion A novel ppoch to optimizg concuent pogm by megg code fom sende with code fom the coespondg eceive. Methods fo educg the ovehed of context switchg. System development A desciption of the implementtion spects of complete nd obust ntive code Elng system tht mkes it possible to test compile optimiztions on el wold pogms. Poofs of the usefulness of this system s esech vehicle by usg the system to evlute egiste lloction sttegies nd diffeent hep chitectues. 1.3 THESIS OVERVIEW The thesis is divided to fou pts, Pefce, Implementtion, Evlution, nd Conclusion. In the est of this fist pt some bckgound mteil is coveed: the lnguge Elng, the gols of the HiPE poject, nd the histoy of developg the HiPE compile. The section on the histoy of HiPE, Section 2.3, lso conts some implementtion detils of vesions pio to the cuent one. Pt II begs with chpte descibg the cuent implementtion of HiPE, Chpte 3. This is followed by desciption of egiste lloctos HiPE, Chpte 4, pesenttion of diffeent hep chitectues Chpte 5, nd pesenttion of pocess optimiztion sttegies Chpte 6. In Pt III, the pefomnce of the HiPE compile, the egiste lloctos, nd the hep chitectues e evluted though benchmkg.

32 1.3. THESIS OVERVIEW 9 In the fl pt of the thesis diections fo futue wok e pesented, some conclusions e dwn nd the thesis is summized. The thesis coves mny diffeent es nd thee is no specific chpte on elted wok; sted discussions of elted wok ppe thoughout the thesis s ppopite.

33

34 Chpte 2 Bckgound Rem tene, veb sequento. Cto In this chpte we pesent bckgound mteil needed fo the undestndg of the m pts of the thesis. This chpte is divided to fou sections: Elng (Section 2.1), Gols of HiPE (Section 2.2), A bief histoy of HiPE (Section 2.3), nd Some specil HiPE fetues (Section 2.4). In the fist section, beside pesentg spects of the Elng lnguge tht fluence the HiPE implementtion, we lso pesent elted wok on memoy chitectues fo concuent lnguges (Section 2.1.2). In the second section we pesent the gols of the HiPE poject nd the HiPE compile, lyg down the philosophy tht hs guided us though the implementtion. Then Section 2.3 we pesent the histoy of the HiPE poject; most of this section sets the bckgound fo the cuent implementtion. This section lso pesents some teestg spects of the HiPE compile, such s the bility to compile one function t the time (Section 2.3.2) nd the use of bckptchg to fcilitte hot-code lodg (Section 2.3.4). The lst section pesents some dditionl fetues the HiPE system tht mkes it possible to stument, pofile, nd mesue diffeent spects of both the untime system nd of Elng pplictions. 2.1 ERLANG Elng 1 is dynmiclly typed, stict, concuent, highe-ode functionl lnguge. The lnguge stted out s n expeimentl implementtion, which hs gown to n dustil implementtion. Thee is no foml defition of the lnguge, but the bsic fetues of Elng e descibed the so clled Elng book ( Concuent pogmmg Elng [10]). Mny new fetues hve been dded to the lnguge 1 Nmed fte the Dnish mthemtic Agne Kup Elng ( ).

35 12 CHAPTER 2. BACKGROUND sce tht book ws witten, nd hence the lnguge is pimily defed by the ltest implementtion fom Eicsson. In this section we will descibe the pts of the lnguge tht e needed fo the undestndg of the est of the thesis. (We will ty to descibe the implementtion dependent spects of Elng, but sce thee is no foml defition nd pciple only one defg implementtion, we will lso descibe some spects tht cn be contibuted s spects of the implementtion.) Elng s bsic dt types e toms, numbes (flots nd bity pecision teges), pocess identifies (o PIDs), efeences, nd bies (byte ys). These dt types cn be combed to the compound dt types lists nd tuples. Thee is no destuctive ssignment of vibles o dt, nd the fist occuence of vible is its bdg stnce. Function ule selection is done with ptten mtchg. Elng heits some ides fom concuent constt logic pogmmg lnguges [83], such s the estiction to flt guds function cluses. Fo pogmmg -the-lge, Elng comes with module system. An Elng module defes numbe of functions. Only explicitly expoted functions my be clled fom othe modules. Clls to functions diffeent modules, clled emote clls, e done by supplyg the nme of the module of the clled function. Tilcll optimiztion is equied fetue of Elng. As othe functionl lnguges, memoy mngement Elng is the esponsibility of the untime system. Elng povides ctch/thow-style exception mechnism fo eo hndlg, ny untime eo such s type eo o division by zeo will esult n exception tht cn be cught by ctch. A simple til-ecusive Elng pogm fo clcultg the length of list might look like Pogm 2.1. Elng pogms execute with n Elng node. Sevel pocesses cn execute concuently on one Elng node, nd sevel nodes cn be connected distibuted netwok. As mentioned, Elng is used five nes high-vilbility (i.e., % of the time vilble) systems, whee downtime is equied to be less thn five mutes pe ye. Such systems cnnot be tken down, upgded, nd estted when softwe ptches nd upgdes ive, sce tht would not espect the vilbility equiement. The pplictions built with Elng e often tended to execute contuously fo yes without exhustg esouces, cshg o stoppg fo ny othe eson. To pefom system upgdg while llowg contuous opetion, n Elng system needs to cte fo the bility to chnge the code of module while the system is unng, so clled hot-code lodg. Pocesses

36 2.1. ERLANG 13 Pogm 2.1 A pogm fo clcultg the length of list. -module(length). %% Defes the nme of the module. -expot([length/1]). %% Expots the function length. %% Retuns the numbe of elements the list List. length(list) -> %% Note, vibles stt with cpitl. length(list,0). %% It is OK to defe sevel functions with the sme %% nme s long s thei ity diffe. %% The length of the empty list ([]) is 0. length([],n) -> 0; %% The length of [_ Rest] is the length(rest) + 1. length([_ Rest],N) -> length(rest,n+1). tht execute old code cn contue to un, but e expected to eventully switch to the new vesion of the module by issug emote cll (which will lwys voke the most ecent vesion of tht module). Once the old code is no longe use, the old module cn be unloded. The Elng lnguge ws puposely designed to be smll, but it comes with lge set of built- functions (known s BIFs) nd big stndd liby. With the Open Telecom Pltfom (OTP) middlewe [88], Elng is futhe extended with liby of stndd solutions to common equiements telecommuniction pplictions (distibuted el-time dtbses, seves, stte mches, pocess monitos, lod blncg), stndd tefces (CORBA), nd stndd communiction potocols (e.g., HTTP, FTP) Concuency Elng Elng is by some clled n cto lnguge [3], sce the concuency is supplied though utonomous pocesses tht communicte synchonously though messge pssg. Pocesses Elng e extemely light-weight, much lighte thn OS o Jv theds [42]. It is not uncommon to hve thousnds of Elng pocesses unng on ech Elng node. The memoy equiements of Elng pocesses my vy dynmiclly dug untime. Elng s concuency pimitives spwn,! (send), nd eceive llow pocess to cete new pocesses nd communicte with othe pocesses though synchonous messge pssg. Tht is, the send opetion is non-blockg, but the eceive is blockg. Note though tht Elng povides mechnism fo llowg pocess to timeout

37 14 CHAPTER 2. BACKGROUND while witg fo messges. (This mkes it possible to implement non-blockg eceive by supplyg timeout of zeo.) Any dt vlue cn be sent s messge nd pocesses my be locted on ny Elng node, i.e., ny mche n Elng netwok. Distibution is hence lmost visible Elng. Ech pocess hs milbox, essentilly messge queue, whee ech messge sent to the pocess will ive. Messge selection fom the milbox occus though ptten mtchg. Thee is no shed memoy between pocesses, o fom diffeent pespective, sce thee e no destuctive updtes Elng ny shg cn neve be obseved. One impotnt fetue of Elng used to suppot obust systems, is pocess lkg, tht is, pocess cn egiste to eceive messge when nothe pocess temtes. It is not necessily the fthe (the spwng pocess) tht eceives this messge nd pocesses cn be mutully lked. This mkes it esy to cete supevisg pocess stuctues tht cn estt cshg pocesses. In the cuent implementtion, pocesses e hndled by the untime system schedule, which selects n Elng pocess fom edy queue. The pocess is ssigned numbe of eductions to execute, clled the time-slice of the pocess. Ech time the pocess does function cll eduction is consumed. The pocess is suspended when the time-slice is used up (i.e., the numbe of emg eductions eches zeo), o when the pocess eches eceive nd thee e no mtchg messges its milbox. In the HiPE system, the schedule is implemented C s function tht cn be clled eithe by the BEAM emulto o diectly fom ntive compiled code. The schedule tkes s guments the pocess tht hs been unng nd the numbe of executed eduction steps, nd etuns the next pocess to execute. Pocesses Elng e not gbge collected Elng objects (lthough the pocess identifies e ecycled). They cn keep on livg even though no othe pocess hs ccess to them. Insted pocess will live s long s it hs code to execute. The untime system keeps fomtion bout pocess pocess contol block o PCB. When pocess dies, its PCB is dellocted Memoy mngement Elng nd othe concuent lnguges As othe functionl lnguges, memoy mngement Elng is esponsibility of the untime system nd hppens though gbge collection.

38 2.1. ERLANG 15 Note tht sce thee e no destuctive updtes, the hep n Elng system is unidiectionl, i.e., thee e no cicul stuctues nd ll potes on the hep lwys pot towd olde objects. The soft el-time concens of Elng cll fo bounded time gbge collection techniques [91, 54]. Amstong nd Vidg popose such technique [9]. This technique, bsed on mk-nd-sweep lgoithm, tkes dvntge of the unidiectionlity of the hep but imposes significnt ovehed nd ws neve fully implemented. In pctice, tuned Elng system with genetionl copyg gbge collecto, gbge collection ltency is usully low (less thn 10 milliseconds) s most pocesses e shot-lived o smll size. Longe puses e quite fequent. Howeve, blockg collecto povides no guntees fo el-time esponsiveness. In the cuent implementtion ll Elng tems e tgged nd t ech gbge collection ll oots e known llowg the system to do pecise gbge collection. Tht mens tht the collecto knows the type of ech tem nd does not need to be consevtive [54]. In the context of stict, concuent functionl lnguge implementtions, thee hs been wok tht ims t chievg low gbge collection ltency without pyg the full pice pefomnce tht gunteed el-time gbge collecto usully equies. Notble mong them is the wok of Doligez nd Leoy [31] who combe fst, synchonous copyg collecto fo the thed-specific young genetions with non-disuptive concuent mk-nd-sweep collecto fo the old genetion (which is shed mong ll theds). The esult is qusi-el-time collecto fo Concuent Cml Light. Also, Lose nd Feeley [35] descibe the design of ne-el-time compctg collecto the context of the Gmbit-C Scheme compile. This gbge collecto ws tended to be used the Elng to Scheme (Etos) system, but to the best of ou knowledge, it hs not yet mde it to n Etos distibution. To chieve low gbge collection puse times, concuent o eltime multipocesso collectos hve lso been poposed; both fo (concuent) vts of ML [47, 67, 24], nd ecently fo Jv [12, 46]. An issue which is to lge extent othogonl to the choice of gbge collection technique is the memoy ogniztion of concuent system: Should one use n chitectue which fcilittes shg, o one tht equies copyg of dt? The issue often ttcts heted debtes both

39 16 CHAPTER 2. BACKGROUND the pogmmg lnguge implementtion community nd elsewhee. 2 We will vestigte this issue futhe Chpte 5. Until the fll of 2001, the Eicsson Elng implementtion hd exclusively pivte hep chitectue, tht is memoy chitectue whee ech pocess lloctes nd mnges its own memoy e. We descibe this chitectue Section 5.1. The m eson why this chitectue ws chosen is tht it is believed it esults lowe gbge collection ltency. As we wnted to vestigte the vlidity of this belief, we hve designed nd implemented shed hep memoy chitectue fo Elng pocesses. We descibe this chitectue Section 5.2; it is ledy cluded the Elng/OTP elese Uses of Elng Elng is cuently used dustilly both by Eicsson Telecom nd by othe compnies fo the development of high-vilbility seves nd netwokg equipment. Some exmples of poducts built usg the Elng/OTP system e: AXD/301, sclble ATM switchg system [17], ANx, n ADSL delivey system [68], switchg hdwe contol system, next-genetion cll cente, nd suite of sclble Intenet seves. Sce 1994, the nnul Elng Use Confeence is the pcipl foum fo epotg wok done Elng nd povides ecod of Elng s evolvg dustil use; dditionl fomtion bout Elng pplictions cn be obted though the elevnt pges t GOALS OF HIPE The m gol of the HiPE poject is to fd genelly pplicble techniques fo efficient implementtions of concuent pogmmg lnguges. Anothe gol is to povide tnsfe of technology fom cdemi to dusty by povidg techniques, which e the esult of cdemic esech, n dustil lnguge implementtion. As mens to tht end we e developg the HiPE compile nd untime system. To use this system to evlute new ides nd techniques the system hs to be complete, so tht el wold pogms cn be used the evlution. It lso hs to be efficient so tht the spects we wnt to evlute e not shdowed by the est of the implementtion. Flly it 2 Fo exmple, the netwokg community n issue which is elted to those discussed this thesis is whethe pckets will be pssed up nd down the stck by efeence o by copyg [4]. Also, dug the mid-80 s the issue of whethe files cn be pssed shed memoy ws vestigted by the opetg systems community the context of use-level kenel extensions, fo exmple the Mch Opetg System [94].

40 2.3. A BRIEF HISTORY OF HIPE 17 hs to be obust nd bug fee so tht we know tht we e mesug the coect behvio. Even though ou im is to fd techniques tht e pplicble to ny pogmmg lnguge nd useful fo the development of ny ppliction, we e concenttg ou effots on the untime pefomnce of Elng nd the type of pplictions pimily developed Elng, nmely lge contol systems. The typicl Elng ppliction is vey dynmic ntue nd hence vey hd to nlyze stticlly with good pecision. We believe tht such pplictions could benefit fom pofile-diven just--time compiltion; hence it is impotnt tht the compiltion times e kept low. Anothe chcteistic of contol pplictions is tht they often consist of huge code bse out of which lge chunk is the code fo opetion nd mtennce, which is not time citicl. Fo this eson we feel tht it is impotnt to hve both compct code fomt combed with efficient, but lge, ntive code. We chieve this by llowg vey smll compiltion units when compilg to ntive code; the use cn fo ech function decide whethe it should be emulted o ntive code. To ech these gols esonble time nd to ensue tht the outcome is dustilly elevnt, we hve bsed ou implementtion on the Elng system povided by Eicsson. This is n dustil stength system tht hs been unde constnt development by tem of engees t Eicsson fo moe thn 10 yes. Ou top-level gols hve esulted thee somewht contdictoy equiements on the HiPE compile: 1) The system should be open nd modul ode to let us plug-nd-ply pts of the system to evlute diffeent implementtion techniques. 2) The compiltion times should be kept low ode to llow fo dynmic compiltion. 3) The system should be complete ode to llow us to use el pogms. The fist equiement hs led to lyeed solution with sevel temedite codes the compile; these will be descibed Chpte 3. The second equiement hs led us to exme techniques such s le scn egiste lloction descibed Chpte 4. This equiement is lso one of the motivtions fo llowg the compiltion of sgle functions. By educg the scope of compiltion the compiltion times cn be educed. The thid equiement hs led to the long nd thoough development of the system, s descibed the next section. 2.3 A BRIEF HISTORY OF HiPE In this section we will descibe the histoy of HiPE, while biefly ddessg some implementtion detils nd the tionle behd some design

41 18 CHAPTER 2. BACKGROUND decisions we took. We divide the desciption to five pts, coespondg to the five mjo evisions of the HiPE system: 1. A fist ttempt, witten C, gve some sight on how to ddess the poblem of efficiently implementg Elng nd showed tht consideble speedup could be chieved usg eltively simple methods. 2. A flexible nd moe esily extensible compile design, mostly witten Elng, mde it possible to expeiment with diffeent optimiztion techniques nd mesue thei impct on some elwold pplictions of Elng. 3. An Open Souce Elng distibution fom Eicsson mde it possible fo HiPE to be publicly elesed, get some uses nd put fom the outside wold. 4. A stong couplg of the HiPE compile with the Elng/OTP system esulted HiPE becomg stndd component Open Souce Elng. 5. Testg, clenup, nd poductifiction ; img t mkg HiPE suppoted component the commecil vesion of Elng/OTP JERICO: The fist pototype The sttg pot of the HiPE system ws Mste s thesis poject the summe of 1996 [49]. The gol ws to develop n optimizg compile, clled JERICO, tht would substntilly impove the pefomnce of Elng pogms. One ppoch tht ws biefly consideed ws to use the Jv Vitul Mche (JVM [60]) s bck-end this ws t the time when Jv ws just sttg to become popul lnguge. It ws soon elized tht the chitectue of the JVM is not well-suited fo dynmiclly typed lnguge such s Elng. The JVM povides no suppot fo tgged dt items, so fo exmple teges hve to be wpped, nd it is wkwd to get pope til-ecusion, which is equied fetue of Elng. In ddition, compilg to JVM implies losg contol ove the efficiency of light-weight theds; fetue citicl fo the pefomnce of typicl Elng pplictions; see lso [42] which compes the pefomnce of Elng pocesses nd Jv theds. Consequently, the ide to compile to JVM ws quickly bndoned nd sted we decided to im fo diect compiltion to ntive code. The chosen chitectue ws SPARC V8; ccodg to Eicsson this ws the most common genel pupose pltfom fo Elng pplictions t the time.

42 2.3. A BRIEF HISTORY OF HIPE 19 We decided to implement ou own bck-end fo sevel esons. Fist nd foemost we wnted system with suppot fo on-the-fly compiltion; system ble to ssemble, lk, nd lod the compiled code diectly to unng system, without hvg to ely on ny extenl pogms. Also sce we need to suppot bckptchg (Section 2.3.4) to llow hotcode lodg we needed fe ged contol ove the object code fomt. A smlle but simil poblem is the hndlg of toms the code. Sce tom vlues e only known t lod time the lode hs to be ble to stntite these vlues. Hvg fe ged contol would lso llows us to do moe dvnced switchg on toms s descibed Section Even if we would hve liked to use some stndd tool fo poducg dynmiclly lked libies the choices wee not tht mny. Usg C s potble ssemble would hve been possible. We did not wnt to ty it though sce it is vey hd to get full nd efficient suppot fo tilecusion C. And to lso mke it wok togethe with emulted code, hot-code lodg, nd gbge collection would be nightme. Anothe possibility would hve been to use ML-RISC [37]. To suppot bckptchg, pecise gbge collection, nd stck mps (Section 3.2.3) we would not hve been ble to use it out of the box without hckg the ML-RISC implementtion. A bck-end solution tht nowdys looks pomisg is C-- [56]. The tention of C-- is to be potble ssemble to be used by compile bck-ends, nd it is tended to supply eveythg needed to hndle both gbge collection nd concuency [77]. Unfotuntely C-- did not exist t the time when we stted the poject. Sce the gol ws to develop compile tht woked fo the complete Elng lnguge nd not just toy compile fo subset of Elng, we decided to bse ou compile on the stble nd wokg Elng untime system mde by Eicsson. At tht time thee wee two Elng systems concuently beg developed t Eicsson: JAM The olde system with stck-bsed bstct mche. BEAM A eltively new system bsed on egiste bstct mche, fluenced by the Wen Abstct Mche (WAM) [92] used mny Polog implementtions. At tht time, the BEAM system hd n option to compile Elng pogms to ntive code vi C [43]; this option ws not vey obust nd ws lte emoved. Both systems used the sme untime system nd simil dt epesenttions [40]. The BEAM system ws quite complex nd not elly stble. Also, t tht time, BEAM hd not poven itself substntilly fste thn JAM. The JAM system on the othe hnd ws quite stble nd significntly simple. Fo exmple, thee whee much less thn 256

43 20 CHAPTER 2. BACKGROUND diffeent byte-code stuctions the JAM, while the BEAM hd ove 400 diffeent stuctions. We decided tht this would be good sttg pot fo ou compile: we could tnslte the geneted JAM byte-code to n tenl temedite epesenttion nd then optimize it befoe genetg ntive code Compile In the Eicsson implementtions of Elng, the smllest unit of compiltion is module, but we decided ely on tht the use o the system should be ble to choose to selectively compile sgle pesumbly time-citicl function t time to ntive code. This wy, the compct epesenttion of emulted byte-code with the efficiency of (usully lge) ntive code cn be combed. This fetue is potentilly vey impotnt fo lge telecom pplictions, whee typiclly only smll potion of the code is time-citicl while the emg code dels with eo coection nd mtennce. The tnsltion fom JAM code to the compile s temedite theeddess code ws done stightfowd wy nd left some oppotunities fo optimiztion. Fo exmple, sce JAM ws stck mche thee would be push ech time vible ws efeenced. This push would be tnslted to egiste copy which would often be unnecessy. To impove code qulity, the JERICO compile pefomed constnt popgtion, constnt foldg, unechble code elimtion, nd ded code emovl [5, 66]. A simple dely slot fille which only looked the bsic block pecedg the bnch fo suitble stuctions ws lso implemented. Registe lloction ws bsed on simple gph colog lgoithm Cllg conventions nd stck fmes The JAM stuction set is simple nd the stuctions cont no fomtion bout the cuent fme size. Insted sevel JAM-mche egistes wee used to keep tck of the loction of locl vibles, guments, nd the stck top. All these potes hd to be sved on the stck t function clls. The ntive code on the othe hnd pssed the fist five guments el mche egistes. Apt fom locl vibles, only the etun ddess ws sved on the stck. The fomt of ntive stck fme is shown Figue 2.1. The JERICO untime system used the sme memoy e fo the ntive nd the JAM stcks, stckg ntive fmes nd JAM fmes on top of ech othe. Smll dummy fmes wee plced between fmes of diffeent types to dicte tnsition between emulted nd ntive