{"id":101444,"date":"2021-09-28T16:22:58","date_gmt":"2021-09-28T14:22:58","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/analiz-vliyaniya-na-proizvoditelnost-vybrannogo-v-sisteme-istochnika-vremeni"},"modified":"2026-02-08T18:56:03","modified_gmt":"2026-02-08T16:56:03","slug":"analiz-vliyaniya-na-proizvoditelnost-vybrannogo-v-sisteme-istochnika-vremeni","status":"publish","type":"post","link":"https:\/\/prohoster.info\/et\/blog\/novosti-interneta\/analiz-vliyaniya-na-proizvoditelnost-vybrannogo-v-sisteme-istochnika-vremeni","title":{"rendered":"Valitud s\u00fcsteemi ajaallika m\u00f5ju anal\u00fc\u00fcs","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Brendan Gregg, \u00fcks DTrace'i arendajatest, kes praegu arendab BPF-p\u00f5hiseid j\u00f5udluse anal\u00fc\u00fcsi t\u00f6\u00f6riistu Linuxi kernelis, on kokkuv\u00f5tlikult jaganud kogemusi, mis saadud j\u00f5udlusprobleemide lahendamisel, millega Netflix silmitsi seisis, kui nad migreerisid andmebaasi Cassandra CentOS-ist Ubuntu-sse Amazon EC2 Xen-i keskkondades. P\u00e4rast migratsiooni suurenes CPU koormus 30% ja umbes sama palju kasvasid ka kirjutamisoperatsioonide latentsus. Selgus, et rakenduste j\u00f5udlus, mis kasutavad intensiivselt aega n\u00f5udvaid p\u00e4ringuid, s\u00f5ltub v\u00e4ga palju valitud s\u00fcsteemi t\u00e4psest ajalooallikast. <\/p>\n

Alguses ei olnud j\u00f5udluse v\u00e4henemise p\u00f5hjus selge ning diagnostika algas s\u00fcsteemiprotsesside j\u00e4lgimisest, mis t\u00f6\u00f6tavad pidevalt v\u00f5i k\u00e4ivitatakse perioodiliselt, kasutades utiliite top ja execsnoop. Kuid k\u00f5ik viitas sellele, et ressursi tarbimine suurenes just Java keeles kirjutatud Cassandra andmebaasis. Kahe Cassandra protsessi, mis t\u00f6\u00f6tasid paralleelselt CentOS-is ja Ubuntu-s ning t\u00f6\u00f6tlesid samu p\u00e4ringuid, profiilide v\u00f5rdlemine n\u00e4itas, et umbes 32% kogu ajast kulub os::javaTimeMillis() \u00fcleskutse tegemiseks, mida kasutatakse praeguse aja teabe saamiseks. <\/p>\n

Seej\u00e4rel viidi l\u00e4bi katse, mille k\u00e4igus kirjutati Java keeles lihtne rakendus, mis kutsus ts\u00fcklis v\u00e4lja meetodi System.currentTimeMillis() sada miljonit korda. Rakenduse k\u00e4itamine n\u00e4itas, et CentOS-i jaoks kulus selle t\u00e4itmiseks 13 sekundit, kuid Ubuntu jaoks \u2014 umbes 68 sekundit, st viis korda aeglasem. Sarnaselt kirjutati C keeles programm, mis kutsus sada miljonit korda v\u00e4lja funktsiooni gettimeofday(), kuid selle k\u00e4itamisel saadi sarnased tulemused. <\/p>\n

Kuna on selge, et probleemi allikaks on praeguse aja tagastamise funktsioon, suunati t\u00e4helepanu erinevate t\u00e4psete ajaallikate valimisel s\u00fcsteemi n\u00e4itajate muutustele. Tundub, et Linuxi k\u00e4ivitamisel kasutati vaikimisi k\u00fclalis\u00fcsteemis taimerit 'xen', nagu n\u00e4htub failist '\/sys\/devices\/system\/clocksource\/clocksource0\/current_clocksource'. Ajaallika muutmisega 'tsc' v\u00e4henes testrakenduse k\u00e4ivitusaeg Ubuntu s\u00fcsteemis 68-lt 3.3 sekundile, st kiirus kasvas 20 korda. Samuti viidi l\u00e4bi kvm-clock ajaallika j\u00f5udlustest, mis n\u00e4itas viivituste suurenemist 20% v\u00f5rreldes TSC-ga. $ cat \/sys\/devices\/system\/clocksource\/clocksource0\/available_clocksource xen tsc hpet acpi_pm $ cat \/sys\/devices\/system\/clocksource\/clocksource0\/current_clocksource xen $ time java TimeBench real 1m8.300s user 0m38.337s sys 0m29.875s $ echo tsc > \/sys\/devices\/system\/clocksource\/clocksource0\/current_clocksource $ time java TimeBench real 0m3.370s user 0m3.353s sys 0m0.026s <\/p>\n

TSC allika valimisel kasutatakse aega saamiseks protsessori instruktsiooni RDTSC, mille t\u00e4itmine ei n\u00f5ua s\u00fcsteemik\u00f5ne tegemist (instruktsioon ei vaja k\u00f5rgendatud \u00f5igusi ja annab v\u00e4\u00e4rtuse CPU-sse sisseehitatud ajaklassi loendurist). Vaikimisi ei aktiveerita TSC, kuna minevikus ei v\u00e4listanud see allikas aja j\u00e4rkj\u00e4rgulist triivimist, mida muudes t\u00f6\u00f6tlejates korrigeeritakse tarkvara abil t\u00e4psemate n\u00e4itude saavutamiseks. Inseneri arvates, kes on spetsialiseerunud protsessorite arendamisele, ei vasta mured TSC kasutamisel aja nihke kohta enam ammu tegelikkusele ja kaasaegsetes protsessorites<\/a> v\u00f5ib see allikas aastaid anda stabiilseid n\u00e4itusid. <\/p>\n

T\u00f6\u00f6de t\u00f5lke serverite<\/a> Netflixi TSC-allika kasutamine v\u00e4hendas salvestusviivitusi 43% ja saavutas Ubuntu kasutamisel tulemusi, mis olid neli korda paremad kui CentOS konfigureerimisega, kus kasutati ajallikaid «xen. Uuringu tulemused edastati ettev\u00f5ttele Amazon, mis soovitas ametlikult AWS EC2 keskkondades Xen h\u00fcperviisoril TSC ajallikat vaikimisi kasutada (Nitro-h\u00fcperviisoril p\u00f5hinevates keskkondades j\u00e4\u00e4b soovitatud kvm-clock).
\n
Allikas: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0411\u0440\u0435\u043d\u0434\u0430\u043d \u0413\u0440\u0435\u0433 (Brendan Gregg), \u043e\u0434\u0438\u043d \u0438\u0437 \u0440\u0430\u0437\u0440\u0430\u0431\u043e\u0442\u0447\u0438\u043a\u043e\u0432 DTrace, \u043d\u044b\u043d\u0435 \u0440\u0430\u0437\u0432\u0438\u0432\u0430\u044e\u0449\u0438\u0439 \u0441\u0440\u0435\u0434\u0441\u0442\u0432\u0430 \u0434\u043b\u044f \u0430\u043d\u0430\u043b\u0438\u0437\u0430 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u0435\u043b\u044c\u043d\u043e\u0441\u0442\u0438 \u043d\u0430 \u0431\u0430\u0437\u0435 BPF \u0432 \u044f\u0434\u0440\u0435 Linux, \u043e\u0431\u043e\u0431\u0449\u0438\u043b \u043e\u043f\u044b\u0442, \u043f\u043e\u043b\u0443\u0447\u0435\u043d\u043d\u044b\u0439 \u0432 \u0445\u043e\u0434\u0435 \u0440\u0430\u0437\u0431\u043e\u0440\u0430 \u043f\u0440\u043e\u0431\u043b\u0435\u043c \u0441 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u0435\u043b\u044c\u043d\u043e\u0441\u0442\u044c\u044e, \u0441 \u043a\u043e\u0442\u043e\u0440\u044b\u043c\u0438 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u044f Netflix \u0441\u0442\u043e\u043b\u043a\u043d\u0443\u043b\u0430\u0441\u044c \u043f\u0440\u0438 \u043f\u0435\u0440\u0435\u0432\u043e\u0434\u0435 \u0421\u0423\u0411\u0414 Cassandra c CentOS \u043d\u0430 Ubuntu \u0432 \u043e\u043a\u0440\u0443\u0436\u0435\u043d\u0438\u044f\u0445, \u0432\u044b\u043f\u043e\u043b\u043d\u044f\u0435\u043c\u044b\u0445 \u0432 \u043e\u0431\u043b\u0430\u043a\u0435 Amazon EC2 \u043d\u0430 \u0431\u0430\u0437\u0435 Xen. \u041f\u043e\u0441\u043b\u0435 \u043c\u0438\u0433\u0440\u0430\u0446\u0438\u0438 \u043d\u0430\u0433\u0440\u0443\u0437\u043a\u0430 […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-101444","post","type-post","status-publish","format-standard","hentry","category-novosti-interneta"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Valitud ajallika m\u00f5ju anal\u00fc\u00fcs s\u00fcsteemi j\u00f5udlusele | ProHoster","description":"Brendan Gregg, \u00fcks DTrace arendajatest, kes praegu arendab BPF-p\u00f5hiseid j\u00f5udluse anal\u00fc\u00fcsi t\u00f6\u00f6riistu Linuxi kernelis, on kokku v\u00f5tnud kogemusi, mida Netflix koges, kui viidi andmebaas Cassandra CentOSilt Ubuntu keskkondadesse, mis t\u00f6\u00f6tavad Amazon EC2 Xen p\u00f5hjal. 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