Virtual machine performance monitoring and fault handling tools

A practical perspective on the world of Virtual machine memory management.

First, the command-line tools of the JDK

The 1.JPS (JVM process Status tool) virtual machine processes health tools.

Displays all of the hotspot virtual machine processes in the development system.

Functionality is single, but most other JDK tools need to enter the Lvmid it queries to determine which virtual machine process to monitor. For the on-premises virtual machine process, the lvmid is consistent with the OS's process ID.

Use: JPS [options] [HostID]

　　

Example:

　　　　

2.jstat (JDK Statistic monitoring Tool) virtual machine Statistics monitor

A command-line tool for monitoring the various health status information for a virtual machine. You can display run-time data such as class loading, memory, garbage Collection, JIT compilation, and so on in a local or remote virtual machine process. No GUI interface. It is the preferred tool for locating virtual machine performance issues at run time.

Jshat format:

jshat [option VIMD [interval [s|ms] [count]]

Vmid: Virtual machine Unique ID, if the local virtual machine process, Vmid is consistent with Lvmid, if the remote virtual machine process, then the VMID format should be:

[Protocol:] [//] lvmid[@hostname [:p ort]/servername].

Interval and count: query interval and number of times. If the two parameters are not queried only once.

Option: On behalf of the user wants to query the virtual machine information, mainly divided into three categories: class loading, garbage collection, run-time compilation status.

　　

Example:

①jstat-class 15043

Displays the number of loaded classes, as well as the occupied space, etc.

　　

Explanation: Loaded (number of loaded classes); Bytes (number of bytes occupied by the load Class), Unloaded (number of unloaded classes), Bytes (the number of bytes unloaded), Time (duration of loading and unloading of classes)

②JSTAT-GC 15043

You can display GC information, the number of times the GC is viewed, and the time.

Explain:

Td>ou

s0c	first survivor Capacity-bytes
s1c	capacity of second survivor
s0u	The first survivor has now made Space
s1u	second survivor currently used space
EC	eden capacity
EU	Eden currently uses space
OC	old generation capacity
old generation has currently used space
PC	perm capacity
PU	Perm currently using space
ygc	from application startup to sampling when GC times in young generation
ygct	from app Time taken by the GC when the program starts to sample (s)
FGC	from application startup to sampling old (full GC) GC times
ygct< /td>	time taken by the GC in the young generation from application startup to sampling (s)
GCT	Total time from application startup to sampling GC (s)

③jstat-gccapacity 15043

can display the use and occupancy of three-generation (Young,old,perm) objects in VM memory

　　　　

Ngcmn	Initial (minimum) size in Young generation (bytes)
Ngcmx	Max capacity of young generation (bytes)
Ngc	Current capacity in young generation (bytes)
s0c	Capacity of the first Survivor (Survivor area) in the Young Generation (bytes)
S1c	Capacity of the second survivor (Survivor area) in the younger generation (bytes)
EC	The capacity of Eden (Eden) in the Young Generation (bytes)
Ogcmn	Initial (minimum) size in old generation (bytes)
Ogcmx	Maximum capacity in old generation (bytes)
OGC	The current newly generated capacity of the old generation (bytes)
Oc	Capacity in old generation (bytes)
Pgcmn	The size (in bytes) of the initialization (minimum) in perm generation
Pgcmx	Maximum capacity of the perm generation (bytes)
Pgc	The current newly generated capacity of the perm generation (bytes)
Pc	Perm (persistent generation) capacity (bytes)
Ygc	Number of GC times in young generations from application startup to sampling
FGC	Old (full GC) GC times from application startup to sampling

④jstat-gcutil 15043 Statistics GC Information the ratio of occupied space to total space

　　

S0	The first survivor (Survivor area) in the younger generation has been used as a percentage of current capacity
S1	The second survivor (Survivor area) of the young generation has been used as a percentage of current capacity
E	Eden (Eden) in the young generation has been used as a percentage of current capacity
O	Percentage of current capacity used by old generation
P	Percentage of current capacity used by perm generation
Ygc	Number of GC times in young generations from application startup to sampling
Ygct	Time taken by the young generation GC from application startup to sampling (s)
FGC	Old (full GC) GC times from application startup to sampling
Fgct	Time (s) used by the old (full GC) GC from application startup to sampling
GCT	Total time (s) used by GC from application startup to sampling

　　

Virtual machine performance monitoring and fault handling tools