???????2?????????????????intel cpu?????????????????????????????????CentOS 6.2????
????1  ??????????MR???????????????????????????????е?job????????????????ganglia?????????????system cpu????30%????????????????????????
????????????
????RHEL 6.2??6.3???а????????????????????“transparent hugepage compaction”??????Hadoop?????????????????????????????????????????????????????Red Hat????δ????????н????????
????????????????????????????????????С?
echo always > /sys/kernel/mm/redhat_transparent_hugepage/enabled
echo never > /sys/kernel/mm/redhat_transparent_hugepage/defrag
????2  ?????????????MR???????????????????????task???????????job????hang?????TT???
2013-08-2006:12:31??050INFO org.apache.hadoop.mapred.TaskLogsTruncater: Initializing logs' truncater withmapRetainSize=-1and reduceRetainSize=-1
2013-08-2006:12:31??053FATAL org.apache.hadoop.mapred.Child: Error running child : java.lang.OutOfMemoryError: unable to create newnative
thread
at java.lang.Thread.start0(Native Method)
at java.lang.Thread.start(Thread.java:640)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier.fetchOutputs(ReduceTask.java:1932)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:382)
at org.apache.hadoop.mapred.Child$4.run(Child.java:270)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1157)
at org.apache.hadoop.mapred.Child.main(Child.java:264)
????????????????????OOM?????????????μ???????????TT??????????????ò?????浼?μ?????
??????????check?????????????????????RHEL 5.4??????Ч??ulimit??nproc????????????в??????Ч?????????ulimit -u??????google??????6.2??????????????????μ????????????/etc/security/limits.d/90-nproc.conf??????Ч??
[hdfs@hd0447-sw40 ~]$ cat /etc/security/limits.d/90-nproc.conf
# Default limit fornumber of user's processes to prevent
# accidental fork bombs.
# See rhbz #432903for
reasoning.
*          soft    nproc     1024
?????????hadoop?????????????????Щ?????????????????????????????????????????????
????1. ???top??????plymouthd????cpu???????
??????????????? /boot/grub/menu.lst ?? ??? “rhgb quiet”?????????? ?????????
????2.power_saving?????????????
?????????????
????????1??rmmod acpi_pad?????????????????????????????
????????2????BIOS?п???ACPI??????????????????2.6.32-358.2.1.el6.x86_64??
????????3????BIOS?????y????
????????4?????????????????????????? /etc/modprobe.d/blacklist.conf????????blacklist acpi_pad??
?????????÷???1???????????????power_saving????????????Щ?????????帺??????????10%?????????????в???power_saving????????÷???4?????????????