bringphysicalmemory

physicalmemory  时间:2021-05-19  阅读:()
Lecture20:CacheHierarchies,VirtualMemoryToday'stopics:CachehierarchiesVirtualmemoryReminder:Assignment8willbepostedsoon(dueTue11/21)ExampleAccessPattern8-bytewords101000Direct-mappedcache:eachaddressmapstoauniqueaddressByteaddressTagCompareDataarrayTagarrayAssumethataddressesare8bitslongHowmanyofthefollowingaddressrequestsarehits/misses4,7,10,13,16,68,73,78,83,88,4,7,10…IncreasingLineSize32-bytecachelinesizeorblocksize10100000ByteaddressTagDataarrayTagarrayOffsetAlargecachelinesizesmallertagarray,fewermissesbecauseofspatiallocalityAssociativity10100000ByteaddressTagDataarrayTagarraySetassociativityfewerconflicts;wastedpowerbecausemultipledataandtagsarereadWay-1Way-2CompareAssociativity10100000ByteaddressTagDataarrayTagarrayHowmanyoffset/index/tagbitsifthecachehas64sets,eachsethas64bytes,4waysWay-1Way-2CompareExample32KB4-wayset-associativedatacachearraywith32bytelinesizesHowmanysetsHowmanyindexbits,offsetbits,tagbitsHowlargeisthetagarrayCacheMissesOnawritemiss,youmayeitherchoosetobringtheblockintothecache(write-allocate)ornot(write-no-allocate)Onareadmiss,youalwaysbringtheblockin(spatialandtemporallocality)–butwhichblockdoyoureplacenochoiceforadirect-mappedcacherandomlypickoneofthewaystoreplacereplacethewaythatwasleast-recentlyused(LRU)FIFOreplacement(round-robin)WritesWhenyouwriteintoablock,doyoualsoupdatethecopyinL2write-through:everywritetoL1writetoL2write-back:marktheblockasdirty,whentheblockgetsreplacedfromL1,writeittoL2WritebackcoalescesmultiplewritestoanL1blockintooneL2writeWritethroughsimplifiescoherencyprotocolsinamultiprocessorsystemastheL2alwayshasacurrentcopyofdataTypesofCacheMissesCompulsorymisses:happensthefirsttimeamemorywordisaccessed–themissesforaninfinitecacheCapacitymisses:happensbecausetheprogramtouchedmanyotherwordsbeforere-touchingthesameword–themissesforafully-associativecacheConflictmisses:happensbecausetwowordsmaptothesamelocationinthecache–themissesgeneratedwhilemovingfromafully-associativetoadirect-mappedcacheVirtualMemoryProcessesdealwithvirtualmemory–theyhavetheillusionthataverylargeaddressspaceisavailabletothemThereisonlyalimitedamountofphysicalmemorythatissharedbyallprocesses–aprocessplacespartofitsvirtualmemoryinthisphysicalmemoryandtherestisstoredondisk(calledswapspace)Thankstolocality,diskaccessislikelytobeuncommonThehardwareensuresthatoneprocesscannotaccessthememoryofadifferentprocessAddressTranslationThevirtualandphysicalmemoryarebrokenupintopagesVirtualaddress8KBpagesizepageoffsetvirtualpagenumberTranslatedtophysicalpagenumberPhysicaladdress13MemoryHierarchyPropertiesAvirtualmemorypagecanbeplacedanywhereinphysicalmemory(fully-associative)ReplacementisusuallyLRU(sincethemisspenaltyishuge,wecaninvestsomeefforttominimizemisses)Apagetable(indexedbyvirtualpagenumber)isusedfortranslatingvirtualtophysicalpagenumberThepagetableisitselfinmemoryTLBSincethenumberofpagesisveryhigh,thepagetablecapacityistoolargetofitonchipAtranslationlookasidebuffer(TLB)cachesthevirtualtophysicalpagenumbertranslationforrecentaccessesATLBmissrequiresustoaccessthepagetable,whichmaynotevenbefoundinthecache–twoexpensivememorylook-upstoaccessonewordofdata!
AlargepagesizecanincreasethecoverageoftheTLBandreducethecapacityofthepagetable,butalsoincreasesmemorywastageTLBandCacheIsthecacheindexedwithvirtualorphysicaladdressToindexwithaphysicaladdress,wewillhavetofirstlookuptheTLB,thenthecachelongeraccesstimeMultiplevirtualaddressescanmaptothesamephysicaladdress–mustensurethatthesedifferentvirtualaddresseswillmaptothesamelocationincache–else,therewillbetwodifferentcopiesofthesamephysicalmemorywordDoesthetagarraystorevirtualorphysicaladdressesSincemultiplevirtualaddressescanmaptothesamephysicaladdress,avirtualtagcomparisoncanflagamissevenifthecorrectphysicalmemorywordispresentCacheandTLBPipelineTLBVirtualaddressTagarrayDataarrayPhysicaltagcomparionVirtualpagenumberVirtualindexOffsetPhysicalpagenumberPhysicaltagVirtuallyIndexed;PhysicallyTaggedCacheBadEventsConsiderthelongestlatencypossibleforaloadinstruction:TLBmiss:mustlookuppagetabletofindtranslationforv.
pagePCalculatethevirtualmemoryaddressforthepagetableentrythathasthetranslationforpageP–let'ssay,thisisv.
pageQTLBmissforv.
pageQ:willrequirenavigationofahierarchicalpagetable(let'signorethiscasefornowandassumewehavesucceededinfindingthephysicalmemorylocation(R)forpageQ)AccessmemorylocationR(findthiseitherinL1,L2,ormemory)Wenowhavethetranslationforv.
pageP–putthisintotheTLBWenowhaveaTLBhitandknowthephysicalpagenumber–thisallowsustodotagcomparisonandchecktheL1cacheforahitIfthere'samissinL1,checkL2–ifthatmisses,checkinmemoryAtanypoint,ifthepagetableentryclaimsthatthepageisondisk,flagapagefault–theOSthencopiesthepagefromdisktomemoryandthehardwareresumeswhatitwasdoingbeforethepagefault…phew!
TitleBullet

pigyun25元/月,香港云服务器仅起;韩国云服务器,美国CUVIP

pigyun怎么样?PIGYun成立于2019年,2021是PIGYun为用户提供稳定服务的第三年,期待我们携手共进、互利共赢。PIGYun为您提供:香港CN2线路、韩国CN2线路、美西CUVIP-9929线路优质IaaS服务。月付另有通用循环优惠码:PIGYun,获取8折循环优惠(永久有效)。目前,PIGYun提供的香港cn2云服务器仅29元/月起;韩国cn2云服务器仅22元/月起;美国CUVI...

PhotonVPS:$4/月,KVM-2GB/30GB/2TB/洛杉矶&达拉斯&芝加哥等

很久没有分享PhotonVPS的消息,最近看到商家VPS主机套餐有一些更新所以分享下。这是一家成立于2008年的国外VPS服务商,Psychz机房旗下的站点,主要提供VPS和独立服务器等,数据中心包括美国洛杉矶、达拉斯、芝加哥、阿什本等。目前,商家针对Cloud VPS提供8折优惠码,优惠后最低2G内存套餐每月4美元起。下面列出几款主机配置信息。CPU:1core内存:2GB硬盘:30GB NVm...

Hostodo:4款便宜美国vps七折优惠低至$13/年;NVMe阵列1Gbps带宽,免费DirectAdmin授权

hostodo怎么样?快到了7月4日美国独立日,hostodo现在推出了VPS大促销活动,提供4款Hostodo美国独立日活动便宜VPS,相当于7折,低至$13/年,续费同价。Hostodo美国独立日活动结束时间不定,活动机售完即止。Hostodo商家支持加密数字货币、信用卡、PayPal、支付宝、银联等付款。Hostodo美国独立日活动VPS基于KVM虚拟,NVMe阵列,1Gbps带宽,自带一个...

physicalmemory为你推荐
formgraph买家google支持ipad支持ipad支付applefusioncharts如何自定义FusionCharts图表上的工具提示?google中国地图求教谷歌中国地图~手机如何使用?google中国地图怎样用GOOLE搜中国地图用卫星看的那一种(可以看到城市和房子的)谷歌sb为什么百度一搜SB是谷歌,谷歌一搜SB是百度?迅雷快鸟迅雷快鸟是做什么用的,,,
vps 域名服务 北京主机租用 winscp enzu 安云加速器 国外服务器网站 http500内部服务器错误 2017年万圣节 世界测速 河南移动m值兑换 双线机房 谷歌台湾 贵阳电信 如何登陆阿里云邮箱 买空间网 江苏双线 网络速度 小夜博客 密钥索引 更多