Jstat command: Problem with JPS jstat command expiration

Take the process of Hadoop as an example, you can view it as a common Java process
1.tmpwatchman Tmpwatch can see that tmpwatch is used to remove some temporary file name that was not used at the time
tmpwatch-removes files which haven ' t been accessed for a period of
Time
OPTIONS
-U,--atime
Make the decision about deleting a file based on the file ' s
Atime (Access time). This is the default.
Note that the periodic UpdateDB file system scans keep the Atime
of directories Recent.
-M,--mtime
Make the decision about deleting a file based on the file ' s
Mtime (modification time) instead of the atime.
-C,--ctime
Make the decision about deleting a file based on the file ' s
CTime (inode change time) instead of the atime; For directories,
Make the decision based on the mtime.
-D,--nodirs
Don't attempt to remove directories, even if they are empty.
-D,--nosymlinks
Don't attempt to remove symbolic links.
The focus here is to see-UMC and-D parameters-umc very clearly access, modify, create time-D parameters do not delete subdirectories, even if they are empty, do not delete symbolic connections
2./etc/cron.daily/tmpwatchcat/etc/cron.daily/tmpwatch can see the Tmpwatch tasks that are scheduled to be performed FLAGS=-UMC
/usr/sbin/tmpwatch "$flags"-x/tmp/. X11-unix-x/tmp/. Xim-unix \
-x/tmp/.font-unix-x/tmp/. Ice-unix-x/tmp/. Test-unix 240/tmp
/usr/sbin/tmpwatch "$flags" 720/var/tmp
For D In/var/{cache/man,catman}/{cat?,x11r6/cat?,local/cat?}; Todo
If [-D "$d"]; Then
/usr/sbin/tmpwatch "$flags"-F 720 "$d"
Fi
Done
This task is executed once a day. Here you see-UMC is set at the same time, if it is set, then take the maximum time, the time in hours in units x indicates the path that needs to be skipped, and these paths will not be deleted. We must have seen the script.
3.jinfo Use the Jinfo command to view a process Jinfo 30352 results are as follows attaching to process ID 30352.
Debugger attached successfully.
Server compiler detected.
JVM version is 20.4-B02
Java System Properties:
Java.runtime.name = Java (TM) SE Runtime Environment
Sun.boot.library.path =/usr/java/jdk1.6.0_29/jre/lib/amd64
Java.vm.version = 20.4-B02
。。。。。。。。。。。。。。。。
File.encoding.pkg = Sun.io
Sun.java.launcher = Sun_standard
User.country = US
Sun.os.patch.level = Unknown
Java.vm.specification.name = Java Virtual Machine specification
User.dir =/home/hadoop/hadoop
Java.runtime.version = 1.6.0_29-b11
Java.awt.graphicsenv = Sun.awt.X11GraphicsEnvironment
Java.endorsed.dirs =/usr/java/jdk1.6.0_29/jre/lib/endorsed
Os.arch = AMD64
Java.io.tmpdir =/tmp
Line.separator =
。。。。。。。。。。。。。。。。。。。。。 Indicates an omission, in which note the Scarlet Letter part Java.io.tmpdir =/tmp represents the temporary output directory of the Java process and generates the process's PID file in/tmp/, and produces the/tmp/hsperfdata_ username Directory I'm here is hadoop-hadoop-jobtracker.pid hsperfdata_root this article link http://www.cxybl.com/html/wyzz/JavaScript_Ajax/20130711/ 39048.html