I would like to know if the output of a Red-Hat based linux could be differently interpreted by a Debian based linux.
To make the question even more specific, what I am after, is understanding how the "load average" from the first line of the
top command on a Red-Hat system is interpreted and how to verify this by official documentation ro code.
[There are many ways to approach this subject, all of which are acceptable answers to the question]
One potential approach, would be to find where this information is officially documented.
Another one, would be to find the code version that
top is built from in the specific distribution and version I am working on.
The command output I am getting is:
top - 13:08:34 up 1:19, 2 users, load average: 0.02, 0.00, 0.00 Tasks: 183 total, 1 running, 182 sleeping, 0 stopped, 0 zombie Cpu(s): 0.2%us, 0.2%sy, 0.0%ni, 96.8%id, 2.7%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 3922520k total, 788956k used, 3133564k free, 120720k buffers Swap: 2097148k total, 0k used, 2097148k free, 344216k cached
In this case how can I interpret the load average value?
I have managed to locate that the average load is about the last minute, from one documentation source and that it should be interpreted after being multiplied with 100, by another documentation source.
So, the question is:
Is it 0.02% or 2% loaded?
Documentation sources and versions:
The first one stars with
TOP(1) Linux User’s Manual TOP(1) NAME top - display Linux tasks
man topin my RedHat distribution
Ubuntu also has the version with "tasks" that does not explain the load average in:
The second one starts with
TOP(1) User Commands TOP(1) NAME top top - display Linux processes
This one starts with:
TOP(1) NAME top - display and update information about the top cpu processes
The first one, can be seen by
man top in
RHEL or in
online ubuntu documentation and it does not have any explanation for the output format (nor about the load average in which I am interested in).
The second one, contains a brief explanation, pointing out that the load average has to do with the last 1 minute, but nothing about the interpretation of its value!
I quote directly from the second source:
2a. UPTIME and LOAD Averages
This portion consists of a single line containing:
program or window name, depending on display mode
current time and length of time since last boot
total number of users
system load avg over the last 1, 5 and 15 minutes
So, if this explanation is indeed correct, it is just enough to understand that the load average is about the last 1 minute.
But it does not explain the format of the number.
In the third explanation, it says that:
When specifying numbers for load averages, they should be multiplied by 100.
This explanation suggests that 0.02 means 2% and not 0.02%. But is this correct? Additionally, is it correct for all distributions of linux and potentially different implementations of
To find the answer to this question, I tried to go through the code by searching it online. But I found, at least, two different version of
top related to RHEL out there! the
builtin-top.c and the refactored
top.c. Both copyrighted by Red-Hat as the notice says in the beginning of the code and thus seems logical that RHEL uses one of these.
So, before delving into that much code, I wanted an opinion about where to focus to form an accurate understanding on how cpu load is interpreted?
From information given in the answers below, in addition to some personal search, I have found that:
topthat I am using is contained in the package procps-3.2.8. Which can be verified by using
- In the version of
procps-3.2.8that I have downloaded from the official website it seems that the tool
uptimeget its information from the
/proc/loadavgdirectly (not utilizing the linux function
- Now for the
topcommand it also does not use the function
getloadavg(). I managed to verify that the
topdoes indeed the same things as the
uptimetool to show the load averages. It actually calls the
uptimetool's function, which gets its information from the
So, everything points to the
/proc/loadavgfile! Thus, to form an accurate understanding of the
load averageproduced by
top, one must read the kernel code to see how the file
There is also an excellent article pointed out in one of the answers that provides a layman's terms explanation of the three values of
So, despite the fact that all answers have been equally useful and helpful, I am going to mark the one that pointed to the article http://www.linuxjournal.com//article/9001 as "the" answer to my question.Thank you all for your contribution!
Additionally from the question Understanding top and load average, I have found a link to the source code of the kernel that points to the spot where
loadavg is calculated. As it seems there is a huge comment explaining the way it works, also this part of the code is in
The link to the code is http://lxr.free-electrons.com/source/kernel/sched/loadavg.c
Again I am not trying to engage in any form of plagiarism, I am just adding this for completeness. So, I am repeating that the link to the kernel code was found from one of the answers in Understanding top and load average.