On 6/11/2023 3:53 pm, Nikhil Agarwal wrote:
Hi David,
Thanks for your reply , It seems top command also uses
/proc/stat to do the magic .Reading a similar issue for top vs another monitor
tool on
https://medium.com/@yogita088/how-to-calculate-cpu-usage-proc-stat-vs-top-e74f99f02d08
, What is the duration for which getProcessCPUload reports CPU utilisation ,
is it from system start time or 1 sec or x seconds ? It is configurable in top
command as -d parameter. This might help to discover difference btw top vs
getprocesscpuload
For getProcessCpuLoad it is the time since the JVM process initialized
the performance counters. At VM init the counters are read from
/proc/stat and /proc/self/stat and stashed away. Then when you ask for
the load the counters are read again and the initial values subtracted
to give the load across the lifetime of the process. You can see the
code here:
https://github.com/openjdk/jdk/blob/master/src/jdk.management/linux/native/libmanagement_ext/UnixOperatingSystem.c
David
regards
Nikhil
-----Original Message-----
From: David Holmes <david.hol...@oracle.com>
Sent: 06 November 2023 10:58
To: Nikhil Agarwal <nikhil.a.agar...@oracle.com>; serviceability-dev@openjdk.org
Subject: Re: getProcessCPULoad returns different CPU percentage as comparead to
top linux command
Hi,
On 3/11/2023 11:50 pm, Nikhil Agarwal wrote:
Hi All,
getProcessCPULoad returns different CPU percentage as
compared to top linux command intermittently . Does it supposed to
returned same data as top command always . Should the
getProcessCPULoad value be same as top/number of cpus always ?
I've no idea how top calculates what it does. The VM reads the first line of
/proc/stat to get the various tick counters.
HTH.
David
regards
Nikhil
