???????磬??????????????????????ZooKeeper??CLDB??MFS??JobTracker??TaskTracker??NFS??the GUI??HBase Master ??HBase RegionServer??????????????????????????????????????????棬????warden????水??????????????????μ??????? ????????map/reduce ????????????????Щ???????60%????5%??????????????35%?????????map/reduce????????????????10G????棬??????3.5G??? map/reduce ??????????? 6??map slot??4??reduce slot????????????????????????JVM??????????350MB??????????512MB????????????map????????????????????????????е?????????Java???????
?????????????????????????????????????????????????????????????swap space???????????????????д????????????????????mapred.map.child.java.opts????“-Xmx500m”????????????????????д????????????????????????ж??????????檔??? map/reduce ?????????????????????????????????????????????????OOM killer??????????????????????????????????????????????????????????????????????????????????????????????JVM??棬??????????????????????????????????????????棬????????????????????????????????????′?????????????????????? ?????????????????????????
????????????????????JVM?????????????????TaskTrackers??????????map/reduce task slot??????
?????????????????????????????????????????в?????????????????????????JobA??????????????????棬????????????????JobB??????????????????檔????????????map/reduce slot????????????????????????????????JobB????task???????????????????????JobA???????????????????????????????????Щ??????????????????????????
???????Э?????????TaskTracker ?????????????????????е? map/reduce tasks ????????????????????????Щ???????????????????????????е???????????????????????????????????????TaskTracker ??????Щ???е???????????棬??????????????????????????????????????????
????????????????????????С????????????????????wordcount?????????“Java????”??????????????????????/opt/mapr/hadoop/hadoop-0.20.2/conf/mapred-site.xml?е??????????? map/reduce ??? slot????????
????mapred.tasktracker.map.tasks.maximum
????mapred.tasktracker.reduce.tasks.maximum
???????????slot???????????С???????????????????????????????????????????JobTracker web??????????????磬??????????TaskTracker ?????????6??mpa slot??4?? reduce slot?????????????? 3??map slot??2?? reduce slot?????????????????????????????TaskTracker?????
????maprcli node services -nodes -tasktracker restart
????????slot?????????????????????wordcount??????????ж??????????????????JVM??????????????檔??????????????????????????????????????????????????????????????????????檔????????????????????????????????????·???????
??????????Java????????????????Щ???裺
??????????????????????????檔
???????TaskTracker ????????????JVM?????????????????????????????
??????????????ЩJVM??????????????????????????д????Щ???á???CPU????????????????????????з???????????????ò??????á?
????????????????????y??????????????????????д?????????
?????????slot?????????С??JobTracker web GUI???????