Difference between Centos 5.5 vs Centos 6/7

[anurag008]

I tried running a binary on both Centos 5.5 and Centos 7.2 with same set of configuration.
I observed that in idle state % of CPU utilization on centos 5.5 was "0.0" while on centos 7.2 it was around "8.0".
Does processes on Centos 7.2 perform some processing even in Idle state?

Thanks

[TrevorH]

Neither one is fit for production use. CentOS 5.5 was released in March 2010 and went out of support when 5.6 was released in January 2011. All of CentOS 5 went EOL in March 2017. Similarly 7.2 was released in November 2015 and became obsolete as soon as 7.3 was released in Nov 2016. The current and only supported version 7 is 7.5.1804. You should yum update to it ASAP.

As for cpu usage, I do not know if you can directly compare one with the other. There are thousands of changes in the kernel between 5 and 7 and I am not sure a direct comparison is useful.

[avij]

TrevorH's remarks are correct, but perhaps there's something that makes that particular process consume more CPU cycles when running under CentOS 7. You could use strace to see if the binary running under CentOS 7 does something unusual. Compare this with the strace output of the binary running under CentOS 5.

[anurag008]

Thanks Avij and Trevor.

@Avij : I tried running strace and found that on centos 7.2 i keep on seeing (futex(0xXXXXXXX, FUTEX_WAKE_PRIVATE, 1) = 0), while on centos 5.5.I didn't see any futex system call.

[jlehtone]

What is function "futex()"?

Code: Select all

man futex

What is FUTEX_WAKE_PRIVATE?
https://lwn.net/Articles/229668/

That article says that *_PRIVATE are used by glibc and your binary probably uses glibc.
It also mentions linux-2.6.21.
CentOS 5 was based on kernel-2.6.18. The kernel and glibc have clearly changed after 2.6.18.


Looking at top/ps on CentOS 7, most processes do show "0.0" CPU usage.

I'd say that it is up to your binary what it does when it is "idle" (GUI app, event loop?),
and how system libraries implement those operations.