Hrtimers and Beyond- Transforming the Linux Time.pdf

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1、HrtimersandBeyond:TransformingtheLinuxTimeSubsystemsThomasGleixnerDouglasNiehauslinutronixUniversityofKansastglx@linutronix.deniehaus@eecs.ku.eduAbstractwillcomplementandcompletethehrtimersandtimeofdaycomponentstocreateasolidfoun-dationforarchitectureindependentsupport

2、ofSeveralprojectshavetriedtoreworkLinuxhigh-resolutiontimersanddynamicticks.timeandtimerscodetoaddfunctionssuchashigh-precisiontimersanddynamicticks.Pre-viouseffortshavenotbeengenerallyaccepted,inpart,becausetheyconsideredonlyasub-1Introductionsetoftherelatedproblemsre

3、quiringaninte-gratedsolution.Theseeffortsalsosufferedsig-Timekeepinganduseofclocksisafundamen-nificantarchitecturedependencecreatingcom-talaspectofoperatingsystemimplementation,plexityandmaintenancecosts.ThispaperandthusofLinux.Clockrelatedservicesinop-presentsadesignwh

4、ichwebelieveprovidesaeratingsystemsfallintoanumberofdifferentgenerallyacceptablesolutiontothecompletecategories:setofproblemswithminimumarchitecturede-pendence.•timekeepingThethreemajorcomponentsofthedesignarehrtimers,JohnStulz’snewtimeofdayapproach,•clocksynchronizati

5、onandanewcomponentcalledclockevents.Clockeventsmanagesanddistributesclock•time-of-dayrepresentationeventsandcoordinatestheuseofclockevent•nexteventinterruptschedulinghandlingfunctions.ThehrtimerssubsystemhasbeenmergedintoLinux2.6.16.Although•processandin-kerneltimersth

6、enameimplies“highresolution”thereisnochangetothetickbasedtimerresolutionat•processaccountingthisstage.JohnStultz’stimeofdayreworkad-•processprofilingdressesjiffyandarchitectureindependenttimekeepingandhasbeenidentifiedasafundamen-talpreliminaryforhighresolutiontimersandT

7、heseservicecategoriesexhibitstronginterac-tickless/dynamicticksolutions.Thispaperpro-tionsamongtheirsemanticsatthedesignlevelvidesdetailsonthehrtimersimplementationandtightcouplingamongtheircomponentsatanddescribeshowtheclockeventscomponenttheimplementationlevel.334•Hr

8、timersandBeyond:TransformingtheLinuxTimeSubsystemsHardwaredevicescapableofprovidingclock2PreviousEffortssourcesvarywi