- Ukuhambisana kwe-cache kuqinisekisa ukuthi wonke amakhophi edatha efanayo kuma-cache ahlukene naku-RAM ahlala ehambisana ezinhlelweni eziningi eziyinhloko.
- Uhlu lwe-cache olunezinga lokugcina elabiwe lwenza kube lula ukulawula ukuvumelana futhi lunciphise ukufinyelela okuqondile kwimemori eyinhloko.
- Amaphrothokholi okuvumelana asebenzisa amasu okungasebenzisi ikhophi noma ukubuyekeza, asekelwa yizimo kanye nama-control bits ngomugqa ngamunye we-cache.
- I-compiler kanye nesistimu yokusebenza kunganezela ukuhambisana kwehadiwe ngokufaka imiyalelo nokulungiselela inkumbulo yezikhathi ezibalulekile.
Uma ubheka umdwebo wanoma iyiphi iprosesa yesimanje enama-core amaningi, iphethini efanayo ihlala ivela: ama-core amaningi, ngalinye linezinqolobane zalo eziseduze, kanye nenqolobane yokugcina ehlanganyelwe esebenza njengephuzu elivamile ngaphambi kokufinyelela ku-RAM. Lokhu kuhlelwa akulona iphutha noma umnqweno wabaklami, kodwa impendulo eqondile enkingeni ebalulekile ezinhlelweni ezifanayo: ukuhambisana kwenqolobane.
Ngaphandle kwendlela eqinile yokuvumelana, umongo ngamunye ungagcina usebenza ngenguqulo ehlukile neyakudala yedatha efanayo kwimemori , okuthi ohlelweni lwangempela luhumushele emaphutheni amancane, ukwehluleka okungalindelekile, ngisho nokuphahlazeka kwesistimu. Ngakho-ke, ukuqonda ukuthi lokhu kuhambisana kugcinwa kanjani—kokubili amazinga ehadiwe nesofthiwe—kuyisihluthulelo sokuqonda ukusebenza kanye nokuzinza kwama-CPU esimanje amaningi.
Kuyini ukuhambisana kwe-cache: isingathekiso sesiphetho
Cabanga ngabantu abaningana behleli phambi kwama-terminal ahlukene, bonke behlela idokhumenti efanayo egcinwe kuseva ephakathi . Isikrini ngasinye sibonisa ikhophi yefayela, futhi noma yiziphi izinguquko ezenziwa ngumuntu oyedwa kulindeleke ukuthi zibonakale ngokushesha ezikrinini zabanye abantu.
Ukuze lokhu kusebenze, kudingeka kube nendlela yokuvumelanisa esakaza izinguquko zedokhumenti kuzo zonke iziphetho, ukuze wonke umuntu ahlale ebona inguqulo efanayo. Uma nje lolu hlelo lusebenza, konke kuhamba kahle: noma ngubani oguqula umbhalo uyazi ukuthi wonke umuntu uzobona inguqulo entsha cishe ngokushesha.
Manje ake ucabange ukuthi uhlelo lokuvumelanisa luhluleka ngokuzumayo. Umuntu ngamunye uyaqhubeka nokuhlela, eqiniseka ukuthi usebenza kudokhumenti eyabiwe, kodwa empeleni, i-terminal ngayinye ishiywa nekhophi yayo yendawo engaxhunyiwe . Kusukela ngaleso sikhathi kuqhubeke, izinguquko ezenziwe ngumuntu oyedwa azifinyeleli kwabanye, futhi idokhumenti iqala ukuhlukana ngokungalawuleki.
Emkhakheni wokubala, yilokhu kanye obekungenzeka uma i-CPU ingenayo iphrothokholi yokuvumelana ethembekile: i-core eyodwa iguqula idatha kwimemori, kodwa amanye ama-core ayaqhubeka nokufunda inguqulo endala kusuka kuma-cache awo ayimfihlo . Lokhu kudala indawo evundile yamaphutha amakhulu anengqondo, idatha eyonakele, kanye nokuziphatha kokususa amaphutha.
Ngakho-ke ukuhambisana kwe-cache kuyisethi yezindlela eziqinisekisa ukuthi, ohlelweni olunezinsika eziningi, wonke amakhophi edatha efanayo asatshalaliswa kuzo zonke izinsika ezihlukene kanye ne-RAM agcina isimo esifanayo . Ngisho noma kukhona amakhophi amaningi, uhlelo kumele luziphathe "njengokungathi" kukhona elilodwa kuphela.
Ama-cache kanye nokuhlelwa kwememori ku-CPU enama-core amaningi
Ama-cache e-CPU ayizinkumbulo ezincane, ezisheshayo kakhulu ezigcina amakhophi ezingcezu ze-RAM ezisetshenziswa njalo . Lapho iprosesa isebenzisa ikhodi, esikhundleni sokufinyelela njalo (i-RAM ehamba kancane uma kuqhathaniswa), izama ukufunda nokubhala ku-cache, okunciphisa kakhulu ukubambezeleka.
Icebo, vele, ukuthi ama-cache awagcini "inguqulo esemthethweni" yedatha, kodwa i-replica yesikhashana kuphela . Ukulandela isifaniso se-terminal, i-RAM ingaba idokhumenti kuseva, kuyilapho ama-cache engaba izikrini zendawo ezibonisa amakhophi ezingxenye ezithile zefayela.
Ku-CPU enama-core amaningi, ukwakheka kuba yinkimbinkimbi kakhulu ngoba i-core ngayinye ivame ukuba nama-cache ayo ayimfihlo e-Level 1 (L1) kanye ne-Level 2 (L2) . Ngaphezu kwalawa, kunezelwa i-cache ye-Level 3 eyabiwe (isibonelo), etholakala phakathi kwama-cores kanye nesilawuli sememori esinikeza ukufinyelela ku-RAM.
Le cache eyabiwe yethulwa ngoba ukuvumela wonke ama-core ukuthi afinyelele i-RAM ngokuqondile nangokujulile kungabangela ukungqubuzana kokufinyelela, impikiswano ngebhasi lememori, kanye nokwehla okukhulu kokusebenza . I-cache yezinga lokugcina isebenza njenge-"buffer" evamile enciphisa ukufinyelela kwe-RAM futhi ibeke phakathi ingxenye enkulu yethrafikhi yedatha.
Ngaphezu kwalokho, izakhiwo eziningi zihlela ama-cache ahlanganisayo: imigqa egcinwe emazingeni aseduze neprosesa nayo ikhona emazingeni aphezulu e-hierarchy . Okusho ukuthi, umugqa ovela ku-L1 nawo uku-L2, futhi, ku-L3. Lokhu kunomphumela owusizo kakhulu wokuvumelana: ukuvuselela nje i-cache esezingeni eliphansi kakhulu kwanele ukulawula isimo samanye amazinga ngaphandle kokufinyelela i-RAM njalo.
Kungani ukugcinwa kwesikhashana okwabiwe kwezinga lokugcina kuyisihluthulelo sokuvumelana
Ngaphandle kwale cache yomhlaba wonke yezinga lokugcina, i-core ngayinye kuzodingeka ihlole ukuvumelana ngqo ne-main memory . Njalo lapho umugqa wememori ku-cache yangasese uguqulwa, kuzodingeka ukuthi kuhlolwe ukuthi amanye ama-core agcina ikhophi yalowo mugqa ofanayo futhi, uma kunjalo, awubuyekeze noma awusebenzise yonke indawo.
Kuhlelo olunama-core amaningi, lo msebenzi wokuhlola uzoholela enanini elikhulu lokuthengiselana ku-RAM , okuzosusa inzuzo enkulu yokuba nama-cache asheshayo. Ngokubeka i-cache eyabiwe phakathi kwama-cores nememori, i-CPU ingagxila ekulawuleni ukuhambisana endaweni eyodwa ephakathi.
Ezintweni eziningi ezisetshenziswayo, ama-cache asezingeni eliphezulu (ngaphandle kweprosesa) aqukethe amakhophi emigqa ekhona emazingeni aseduze ne-core . Ngale nhlangano, iphrothokholi yokubumbana idinga kuphela ukuqinisekisa ukuthi izinga lokugcina livumelaniswa nememori eyinhloko, nokuthi amazinga angasese e-core ngayinye avumelaniswa nezinga elingaphezu kwayo.
Lokhu kungabonakala njengohlobo lwedoli laseRussia lokuzalela: i-cache yezinga lesithathu ifaka okuqukethwe kweleveli yesibili neyokuqala , izinga lesibili lifaka okuqukethwe kwalo kanye nokwezinga lokuqala, kanti izinga lokuqala lazi imigqa yalo kuphela. Ngakho-ke, ngokulawula "idoli elikhulu" (izinga lokugcina), uhlelo lungahlanganisa okunye kahle kakhulu.
Umphumela uba ukuthi ukugcina ukuhambisana kuba ngcono ngokwendlela yokuklama kanye nethrafikhi yememori . Esikhundleni sokuphoqa i-core ngayinye ukuthi ibhekane ne-RAM njalo, iphrothokholi isebenza ku-cache eyabiwe futhi kusukela lapho ilawula ukuthi yimiphi imigqa okufanele ibuyekezwe noma ingasebenzi kuma-cache ayimfihlo.
Izindlela zokuvuselela: ukungasebenzi kanye nokuvuselelwa kwamakhophi
Inkinga ebalulekile iphakama lapho ama-core amabili noma ngaphezulu efuna ukufinyelela, cishe ngasikhathi sinye, umugqa ofanayo wedatha ophindaphindwayo kuma-cache amaningi . Kulesi simo, izinhlelo zokuvumelana zivame ukusebenzisa amasu amabili ayisisekelo lapho kuphathwa ukubhala.
Indlela yokuqala isekelwe ekungavumeleki. Uma i-kernel idinga ukubhala kumugqa we-cache othize, iphrothokholi ivimbela noma yimaphi amakhophi alowo mugqa ofanayo angase abe khona kwamanye ama-cache . I-kernel ezobhala kuphela egcina umugqa esimweni sokufunda nokubhala; abanye, uma befuna ukusebenzisa leyo datha futhi, kuzodingeka balayishe kabusha umugqa kusukela ezingeni eliphezulu (noma kusuka kwimemori) ngenguqulo ebuyekeziwe.
Isu lesibili lihilela ukubuyekeza. Kulesi simo, lapho i-kernel iguqula umugqa, uhlelo luzama ukusabalalisa ngokuzenzakalelayo okuqukethwe okusha kumakhophi akhona kwamanye ama-cache . Ngale ndlela, wonke ama-cache agcine lowo mugqa athola inguqulo ebuyekeziwe ngaphandle kokudinga ukuyivala bese eyilayisha kabusha kamuva.
Indlela ngayinye inezinzuzo nezingozi zayo. Ukungasebenzi kahle kuvame ukusebenza kahle kakhulu uma ukubhala kuvame ngoba kugwema ukugcwala uhlelo lwememori ngezibuyekezo ezinye izinhlayiya ezingase zingazidingi ngokushesha. Ngakolunye uhlangothi, ukuvuselela kungaba nenzuzo lapho izinhlayiya eziningi zifunda njalo idatha efanayo eguqulwa kaningi , njengoba kunciphisa ukubambezeleka ngokungadingi ukulayisha kabusha umugqa ngemva kokungasebenzi kahle ngakunye.
Kunoma ikuphi, zombili izindlela zisebenzisa izimo ezengeziwe kanye nama-control bits emigqeni ye-cache. Umugqa ngamunye uvame ukufaka ulwazi mayelana nokuthi okuqukethwe kwawo kuyafana yini nalokho okuku-RAM , nokuthi ngabe kwabelwana ngakho, kushintshiwe, kukhethekile, kugodliwe, njll., kuye ngephrothokholi ethile (i-MESI, i-MOESI, i-MSI, njll.). Lokhu kuvumela ihadiwe ukuthi yenze izinqumo ezisheshayo mayelana nokuthi yini okufanele yenze lapho kwenzeka umsebenzi wokufunda noma wokubhala emgqeni osuvele uphindaphindiwe.
Ukuhlola ukuvumelana phakathi kwama-cache nememori
Ukuqinisekisa ngokuqondile ukuvumelana phakathi kwawo wonke amazinga e-cache e-CPU noma i-GPU kanye nememori eyinhloko kungaba umsebenzi omkhulu, kokubili maqondana nobunzima bokuklama kanye nezindleko zokusebenza. Ngakho-ke, izinhlelo zanamuhla zihlela lokhu kuqinisekiswa ngokulandelana.
Ama-cache aseduze neprosesa (L1, L2) awavami ukuxhunywa ngqo kwi-RAM, kodwa axhunywa ezingeni elilandelayo le-cache. Lokhu kusho ukuthi ukuvumelana akuqinisekisiwe ngokumelene nememori eyinhloko kuzo zonke izinga, kodwa kunalokho ngokumelene nezinga eliphakeme kakhulu . Lokhu kunciphisa inani lokufinyelela kwe-RAM futhi kwenza kube lula ukuqonda okudingekayo emazingeni aphansi.
Ekugcineni, ukuqhathanisa phakathi kokuqukethwe kwe-cache nokuqukethwe kwe-RAM kwenziwa phakathi kwe -cache yezinga lokugcina nememori eyinhloko . Uma leli zinga lokugcina ligcina isimo esifanele nesihambisanayo, futhi izinga ngalinye eliphansi ligcina ukuvumelana kwalo nelingaphezulu kwalo, lonke uhlu luhlala luhambisana ngaphandle kokuhlola umugqa ngamunye ngokumelene ne-RAM ngokuphindaphindiwe.
Uma i-kernel ibhalela umugqa we-cache futhi ishintsha idatha yayo, isimo salowo mugqa simakwa ukuze sibonise ukuthi ayisafani ncamashi nekhophi egcinwe kwimemori . Ukusuka lapho, iphrothokholi ihlanganisa isibuyekezo: imaka amakhophi ahambisanayo kwamanye ama-cache njengagodliwe noma angavumelekile futhi, uma kufaneleka, ibhala okuqukethwe okusha kumugqa wememori oyinhloko ohambisanayo.
Le nhlangano yokuqhekeka ivumela izinguquko ukuthi zisakazeke kancane kancane kusukela ku-kernel, evuselela idatha, iye kwimemori eyinhloko, idlule ezingeni ngalinye le-cache ngendlela elawulwayo. Ngale ndlela, ukugcina ukuvumelana akube yisithiyo esingenakunqotshwa seprosesa.
Ukuhambisana kwehadiwe uma kuqhathaniswa nokuhambisana kwesofthiwe
Kuze kube manje sesixoxe ngezindlela zokuvumelana ezisetshenziswa kakhulu kwihadiwe: amaphrothokholi, ama-status bits, ama-cache abiwe, njll. Kodwa-ke, kunenye indlela efuna ukushintshela okunye kwalokhu bunzima kusofthiwe , ikakhulukazi ku-compiler kanye nesistimu yokusebenza.
Izinhlelo zokuvumelana ezisekelwe kusofthiwe zizama ukunciphisa isidingo se-logic eyengeziwe ye-on-chip ngokuhlaziya ikhodi nokwenza izinqumo zesikhathi sokuhlanganisa . Umqondo uwukuthi uma i-compiler inganquma ukuthi idatha ethile eyabiwe ifinyelelwa nini futhi kanjani, ezimweni eziningi, ingavimbela leyo datha ukuthi igcinwe noma iphathe ngokusobala ukubonakala kwayo.
Le ndlela inenzuzo ecacile: ingxenye yomsebenzi ishintsha kusukela ku-running time kuya ku-compile-time resolution . Esikhundleni sokuthi i-hardware ithole futhi iphathe zonke izingxabano ngokushesha, i-compiler izama ukuzibona kusengaphambili futhi ikhiqize ikhodi egwema izimo eziyingozi.
Okubi ukuthi ukuhlaziywa kwekhodi engaguquki kunqunyelwe, ngakho-ke abahlanganisi bavame ukuba ngabagcinayo . Lokhu kusho ukuthi, ukuze bagweme ukwephula ukuvumelana, bavame ukwenza izinqumo ezinciphisa ukusebenza kahle kwezilondolozi. Uma besola ukuthi idatha ethile ingaba yinkinga, bavame ukuyivimbela ukuthi igcinwe noma baphoqelele ukuvumelanisa kaningi kunalokho okudingekile.
Ngakho-ke, yize lezi zinhlelo zesofthiwe zikhanga ngokwethiyori, ikakhulukazi ekwenzeni lula ukwakheka kwehadiwe, empeleni azithathi indawo yokusekelwa kokuhambisana okuhlanganiswe ne-CPU uqobo , kodwa kunalokho ziyayigcwalisa kwezinye izimo ezithile.
Indima yomhlanganisi ekuhambisaneni kwe-cache
Isici esibalulekile sezindlela zokuvumelana ezisekelwe kusofthiwe yindima yomhlanganisi. Umhlanganisi angenza ukuhlaziywa okujulile kwekhodi futhi anqume ukuthi yiziphi izakhiwo zedatha ezabiwe ezingase zingaphephile ekugcinweni kwedatha . Ngokusekelwe kulokhu, uphawula lezi zinto ngendlela ekhethekile noma aguqule ukukhiqizwa kwekhodi.
Indlela elula, futhi elondolozayo kakhulu, ukuvimbela iziguquguquko zedatha ezabiwe ukuthi zingagcinwa ku-cached . Okusho ukuthi, ukufinyelela ngakunye kwalezi ziguquguquko kuphoqa ukufinyelela kwimemori eyinhloko noma endaweni engagcinwa. Lokhu kuqinisekisa ukuvumelana, kodwa kuphuthelwa amathuba amaningi okusebenza, ngoba isakhiwo esabiwe, empeleni, singasetshenziswa ngasese ngezikhathi ezithile, noma sifundwe kuphela kwezinye.
Eqinisweni, inkinga yokungaguquguquki ivela kuphela ngezikhathi lapho okungenani inqubo eyodwa ingabhalela ku-variable kanti enye inqubo ingayifunda . Ngaphandle kwalezi zikhathi ezibucayi, i-variable ingaphathwa njengokusetshenziswa okukhethekile kwentambo eyodwa noma ngisho njengento eqhubekayo esebenzayo isikhashana, okuvumela ukuthi igcinwe ngaphandle kwezinkinga.
Amasu okuhlanganisa athuthuke kakhulu azama ukuhlonza lezo zikhathi "eziphephile" lapho i-variable eyabiwe ingabhekwa njengengangqubuzani . Ukuze yenze lokhu, i-compiler ihlaziya izindlela zokwenza, ukufinyelela okungenzeka ngesikhathi esifanayo, kanye namaphethini okuvumelanisa (ukukhiya, izingxenye ezibucayi, njll.). Ngokusekelwe kulokhu kuhlaziywa, ihlukanisa isikhathi sokuphila kwe-variable ngezigaba: ezinye zifanelekela ukugcinwa kwesikhashana, ezinye zidinga ukuphathwa okukhethekile.
Phakathi nezikhathi ezibucayi, lapho ukufinyelela ngasikhathi sinye nokubhala kutholwa, i-compiler ifaka imiyalelo eyengeziwe kukhodi ekhiqiziwe ukuze iphoqelele ukuhambisana kwe-cache . Le miyalelo ingaphoqa ukugeleza kwe-cache, ukulayisha kabusha imemori, izithiyo zememori, noma ukufinyelela ezifundeni eziphawulwe njengezingenakuvinjelwa, kuye ngemodeli yokuhlela kanye nokwakheka okungaphansi.
Ubudlelwano phakathi komhlanganisi, isistimu yokusebenza, kanye nehadiwe
Inkulumo ethi "umhlanganisi ufaka imiyalelo kukhodi ekhiqiziwe ukuze kuqinisekiswe ukuhambisana kwe-cache" ingase yenze umuntu acabange ukuthi uhlelo lokusebenza lufunda le miyalelo njengokungathi iyizinkomba zezinga eliphezulu futhi, ngokusekelwe kulokho, lunquma ukuthi luzoqhutshwa kanjani uhlelo. Eqinisweni, indlela yokusebenza ihlukile kancane.
Uma i-compiler ingeza lezi zinhlobo zemiyalelo, lokho ekwethula ku-binary imisebenzi ethile esekelwa yisakhiwo noma indawo yokusebenza kwesikhathi . Isibonelo, ingafaka imiyalelo yokususa i-cache, izithiyo zememori, imiyalelo ekhethekile yokumaka izifunda njengezingenakuvinjelwa, noma izingcingo kumasevisi esistimu yokusebenza alungiselela izimfanelo zememori.
Uhlelo lokusebenza aluchazi le miyalelo njenge "amazwana" noma "amacebo" asezingeni eliphezulu abhalwe yi-compiler; lumane lusebenzise ikhodi yomshini njenganoma iyiphi enye . Kodwa-ke, eminye yale miyalelo yenzelwe ukusebenzisana nesistimu yememori kanye nokuphathwa kwe-cache, ngaleyo ndlela kushintshe indlela i-CPU efinyelela ngayo idatha ethile.
Ngamanye amazwi, i-compiler yenza ukuhlaziywa kokuqala futhi ikhiqiza ikhodi, lapho isetshenziswa, ekhiqiza ukuziphatha kwe-cache okufiswayo . Uhlelo lokusebenza lusebenzisana ngokusungula izimfanelo zememori (izindawo ezigciniwe noma ezingagciniwe, izinqubomgomo zokubhala, njll.) kanye nokunikeza ama-primitive okuvumelanisa, kodwa akuyona "ukufunda" imiyalelo ekhethekile ngomqondo wokuyihumusha ngokwesisho njengoba i-compiler ibingenza.
Kungenzeka futhi ukuthi ihadiwe, lapho ibona imiyalelo ethile, isebenze ukuhambisana okuthile noma izindlela zokuvumelanisa . Isibonelo, imiyalelo yocingo noma yokuvimba iqinisekisa ukuhleleka kokufinyelela kwimemori futhi iphoqelele imiphumela ethile yokubonakala kulo lonke uhlu lwezinqolobane. Kulesi simo, kukhona ukubambisana okunezindlela ezintathu: umqoqi unquma ukuthi uzobeka kuphi le miyalelo, uhlelo lokusebenza lulungiselela indawo yokusebenza, futhi ihadiwe isebenzisa ukuziphatha kwangempela ezingeni le-cache kanye nebhasi lememori.
Zonke lezi zinto ziqinisekisa ukuthi, ngisho noma kunamakhophi amaningi edatha efanayo asatshalaliswa kuma-cache ahlukene kanye nememori eyinhloko, izinhlelo ezifanayo zisebenza ngemodeli yememori ehambisanayo . Ukuhambisana kwe-cache, hhayi nje ukuba imininingwane yangaphakathi ye-CPU elula, kuba yingxenye ebalulekile yezinhlelo ze-multi-core ukuze zisebenze ngokuthembeka nangokusebenza kahle.
Ukuqonda ukuthi ukuhlelwa kwe-cache, amaphrothokholi okuhambisana kwehadiwe, kanye namasu okusekela isofthiwe kuhlangana kanjani kwenza kucace ukuthi kungani imiklamo ye-CPU yesimanje inesakhiwo esifanayo, nokuthi kungani ukwehluleka okuncane kunoma iyiphi yalezo zindlela kungabangela ukuziphatha okuphazamisayo ezinhlelweni zokusebenza ezihambisanayo ezincike ngokuphelele kuzo zonke izinhla ezibona idatha efanayo ngesikhathi esifanele.