V\u00fdvoj\u00e1\u0159i projektu Multikernel, kter\u00fd umo\u017e\u0148uje na jednom fyzick\u00e9m po\u010d\u00edta\u010di provozovat n\u011bkolik nez\u00e1visl\u00fdch instanc\u00ed j\u00e1dra bez hypervizoru a virtualizace, p\u0159edstavili n\u00e1stroj kmorph, kter\u00fd implementuje prost\u0159edky pro rychl\u00e9 obnoven\u00ed po havarijn\u00edm ukon\u010den\u00ed j\u00e1dra Linuxu nebo pro v\u00fdm\u011bnu j\u00e1dra v re\u017eimu Live bez \u00fapln\u00e9ho restartu. Projekt vede Cong Wang, kter\u00fd spravuje pod syst\u00e9m \u0159\u00edzen\u00ed provozu (TC, Traffic Control) v j\u00e1dru. Metoda rychl\u00e9ho restartu je zalo\u017eena na p\u0159edb\u011b\u017en\u00e9m na\u010dten\u00ed z\u00e1lo\u017en\u00edho j\u00e1dra do pam\u011bti, kter\u00e9 nahrazuje hlavn\u00ed pracovn\u00ed j\u00e1dro v p\u0159\u00edpad\u011b selh\u00e1n\u00ed nebo p\u0159i pot\u0159eb\u011b v\u00fdm\u011bny j\u00e1dra za novou verzi. <\/p>\n
Navrhovan\u00fd p\u0159\u00edstup umo\u017e\u0148uje ob\u011b\u017een\u00ed bez \u00fapln\u00e9ho restartu a t\u00e9m\u011b\u0159 okam\u017eit\u00e9 obnoven\u00ed provozu, \u010d\u00edm\u017e se minimalizuje doba prostoj\u016f. V sou\u010dasn\u00e9 dob\u011b, v p\u0159\u00edpad\u011b havarijn\u00edho ukon\u010den\u00ed \u010dinnosti j\u00e1dra, trv\u00e1 \u00fapln\u00fd restart v\u011bt\u0161\u00edch servery<\/a> Zab\u00edr\u00e1 to n\u011bkolik minut vzhledem k dlouh\u00fdm proces\u016fm inicializace za\u0159\u00edzen\u00ed, na\u010d\u00edt\u00e1n\u00ed syst\u00e9mov\u00e9ho prost\u0159ed\u00ed a ulo\u017een\u00ed pam\u011b\u0165ov\u00e9ho dumpu j\u00e1dra prost\u0159ednictv\u00edm mechanismu kdump. V podstat\u011b p\u0159i pou\u017eit\u00ed kdump doch\u00e1z\u00ed k dv\u011bma restart\u016fm j\u00e1dra \u2014 nejprve se pomoc\u00ed kexec na\u010dte samostatn\u00fd instance j\u00e1dra pro ulo\u017een\u00ed pam\u011b\u0165ov\u00e9ho dumpu, pot\u00e9 dojde k na\u010dten\u00ed pracovn\u00edho j\u00e1dra a spu\u0161t\u011bn\u00ed syst\u00e9mov\u00fdch slu\u017eeb.<\/p>\n V p\u0159\u00edpad\u011b pou\u017eit\u00ed kmorph v p\u0159ipojen\u00ed k samostatn\u00e9mu CPU j\u00e1dru se do pam\u011bti p\u0159edem na\u010dte z\u00e1lo\u017en\u00ed j\u00e1dro Linuxu a minim\u00e1ln\u00ed syst\u00e9mov\u00e9 prost\u0159ed\u00ed, kter\u00e9 sleduje stav hlavn\u00edho j\u00e1dra. V p\u0159\u00edpad\u011b zamrznut\u00ed nebo vstupu do stavu paniky hlavn\u00edho j\u00e1dra p\u0159evezme z\u00e1lo\u017en\u00ed prost\u0159ed\u00ed kontrolu, ulo\u017e\u00ed pam\u011b\u0165ov\u00fd dump selh\u00e1vaj\u00edc\u00edho j\u00e1dra, p\u0159epne na sebe procesorov\u00e1 j\u00e1dra, pam\u011b\u0165, za\u0159\u00edzen\u00ed, s\u00ed\u0165ovou konfiguraci a FS. <\/p>\n P\u0159ep\u00edn\u00e1n\u00ed se koordinuje pomoc\u00ed dvou program\u016f: kmorph \u2014 spou\u0161t\u00ed se v aktivn\u00edm prost\u0159ed\u00ed, vytv\u00e1\u0159\u00ed obsah z\u00e1lo\u017en\u00edho prost\u0159ed\u00ed a synchronizuje v n\u011bm stav s\u00edt\u011b; kmorphd \u2014 spou\u0161t\u00ed se v z\u00e1lo\u017en\u00edm prost\u0159ed\u00ed a sleduje stav aktivn\u00edho prost\u0159ed\u00ed. Krom\u011b p\u0159ep\u00edn\u00e1n\u00ed v p\u0159\u00edpad\u011b hav\u00e1rie existuje mo\u017enost vyu\u017eit\u00ed kmorph pro aktualizaci j\u00e1dra bez tradi\u010dn\u00edho restartu. Pro urychlen\u00ed obnovy v z\u00e1lo\u017en\u00edm prost\u0159ed\u00ed, krom\u011b j\u00e1dra a minim\u00e1ln\u00ed sady syst\u00e9mov\u00fdch komponent, mohou b\u00fdt v pohotovostn\u00edm re\u017eimu spu\u0161t\u011bny typov\u00e9 slu\u017eby, jako je nginx. V tomto p\u0159\u00edpad\u011b bude p\u0159i aktivaci z\u00e1lo\u017en\u00edho prost\u0159ed\u00ed slu\u017eba nginx ji\u017e na\u010dtena do pam\u011bti a okam\u017eit\u011b za\u010dne zpracov\u00e1vat po\u017eadavky po p\u0159epnut\u00ed do nov\u00e9ho prost\u0159ed\u00ed s\u00ed\u0165ov\u00e9 karty, aktivaci s\u00ed\u0165ov\u00e9 konfigurace a zm\u011bn\u011b ko\u0159enov\u00e9ho FS.<\/p>\n Ve proveden\u00fdch testech server s nginx pomoc\u00ed kmorph obnovuje \u010dinnost p\u0159ibli\u017en\u011b 2 sekundy po selh\u00e1n\u00ed j\u00e1dra, ale v budoucnu se pl\u00e1nuje dos\u00e1hnout okam\u017eit\u00e9ho p\u0159epnut\u00ed, kter\u00e9 bude neviditeln\u00e9 pro p\u0159ipojen\u00e9 klienty. V sou\u010dasn\u00e9 dob\u011b kmorph podporuje architektury x86_64 a ARM64, a tak\u00e9 se pracuje na podpo\u0159e RISC-V. Integrace kmorph do distribuc\u00ed Linuxu se uskute\u010d\u0148uje analogicky s podporou kdump, prost\u0159ednictv\u00edm standardn\u00edch n\u00e1stroj\u016f dracut, initramfs-tools, kernel-install a slu\u017eby systemd.<\/p>\n