What does it mean, when a CPU usage of a core is 100 percent?
Does it mean that a process has peaked the maximum possible performance of a core (with vectorization) or does it mean that the CPU is doing as many cycles as the core clock is?
Also, if it is 100 percent, can I imply that the process is CPU bound, i.e. a faster and bigger Cache, Memory, bus, etc. will not make any difference?
CPU usage usually means: What fraction of real time is the CPU doing any work. 90% CPU usage means that the CPU is 90% busy and 10% idle. When the CPU is idle it is doing nothing and it just waits for interrupts.
In this view the CPU always includes the caches and the memory. A bigger cache and a faster memory will always make your CPU work faster in this sense.
A CPU usage of 100% means that the processes are in sum CPU bound. They would run faster if the CPU would be faster.
A CPU usage of less than 100% means that the processes are in sum I/O bound. They would not run faster if the CPU would run faster.
Related
I've begun to track my asp.net application metrics, but for Servers -> Process CPU (avg) I'm getting values above 100% (194% or more). What does that mean?
Probably it means it's a multi-threaded process that's keeping 1.94 CPUs busy, on average.
Is it possible to limit CPU & Memory for the *nix Process?
The CPU limit may look like "use no more than 10% of one core".
The memory limit may look like "use no more than 100Mb", the OS may limit it or kill the process if it try to exceed the limit, both ways are fine.
Any *nix that could do that would be fine.
It seems it is possible to implement it with virtual machines, but it is not acceptable because the overhead is too huge.
If you happen to use Solaris, the ability to limit resource usage is a native feature.
Memory (RAM) usage can be capped per process using the rcap.max-rss setting while CPU usage can be limited per project using the project.cpu-caps.
Note that Solaris also allows OS level virtualization (a.k.a. zones) which have no significant overhead, if any, compared to a bare metal OS instance.
Resource capping is part of Solaris zones configuration.
Try CPULimit
cpulimit is a simple program which attempts to limit the cpu usage of a process (expressed in percentage, not in cpu time). This is useful to control batch jobs, when you don't want them to eat too much cpu. It does not act on the nice value or other scheduling priority stuff, but on the real cpu usage. Also, it is able to adapt itself to the overall system load, dynamically and quickly.
We have a process that is computationally intensive. When it runs it typically it uses 99% of the available CPU. It is configured to take advantage of all available processors so I believe this is OK. However, one of our customers is complaining because alarms go off on the server on which this process is running because of the high CPU utilization. I think that there is nothing wrong with high CPU utilization per se. The CPU drops back to normal when the process stops running and the process does run to completion (no infinite loops, etc.). I'm just wondering if I am on solid ground when I say that high CPU usage is not a problem per se.
Thank you,
Elliott
if I am on solid ground when I say that high CPU usage is not a problem per se
You are on solid ground.
We have a process that is computationally intensive
Then I'd expect high CPU usage.
The CPU drops back to normal when the process stops running
Sounds good so far.
Chances are that the systems you client are using are configured to notify when the CPU usage goes over a certain limit, as sometimes this is indicative of a problem (and sustained high usage can cause over heating and associated problems).
If this is expected behavior, your client needs to adjust their monitoring - but you need to ensure that the behavior is as expected on their systems and that it is not likely to cause problems (ensure that high CPU usage is not sustained).
Alarm is not a viable reason for poor design. The real reason may be that it chokes other tasks on the system. Modern OSes usually take care of this by lowering dynamic priority of the CPU hungry process in such a way that others that are less demanding of CPU time will get higher priority. You may tell the customer to "nice" the process to start with, since you probably don't care if it runs 10 mins of 12 mins. Just my 2 cents :)
we have requirement to handle 10000 concurrent user.
Let me explain the system. Machine has two processors. ProcessModel in machine.config is set as autoconfig = true. so that makes maxWorkerThreads = 20.
When I Load run my case with 30 users and watch CPU usage it is maximing to 100. and number of threads on w3wp.exe is more then 70. As my default is 20 * 2 (CPU's) = 40.
Once cpu touches 100% most of the transaction fail or talking maximum time to respond
Now questions
1. how do i get 30 more threads assigned to the same workerprocess?
2. How can reduce CPU usage here?
You have a bit of an issue here. Increasing the # of threads will further increase CPU usage. (Your 2 goals are incompatible.) Not only are you asking each CPU to do more, but you'll have additional overhead with context switching.
You could investigate using a non-blocking IO library, which would essentially mean only 1-2 threads per CPU. However, this could be a significant architecture change to your project (probably not feasible) - and what you might actually find is that most of the CPU was actually spent due to the work your code is performing, and not because of anything threading-related.
It sounds like you need to do some performance tuning and optimization of your application.
You should take a look at making async calls so that your threads are not remaining active while the caller is waiting for a response.
http://msdn.microsoft.com/en-us/magazine/cc163463.aspx
I'm trying to recognize a run away threads in my own application and close them for good before they render machine inaccessible.
However, I can only get CPU time for the thread, that is limitation of API I'm using. Is there any way to evaluate CPU utilization from that data?
I was thinking about comparing it to real time and if it is close - than that thread is loading CPU too much. What do you think about that heuristic, will it work?
CPU time divided by real time will give you CPU utilization.