WP7 , High CPU Utilization - performance

I am building a WP7 application.
I noticed high cpu utilization using the Performance Monitoring tool.
Even a simple hello world application gives High CPU utilization.
This happens in the UI Thread.
How do we get the application to use less then 50 % of the CPU ?
This image is that of the hello world application. We can see the the graph is easily above 50%.
Is that an area of concern ?

In isolation a single measurement of an application starting up and taking, for a short while, more than 50% of CPU time is not a matter of concern.
One way to make the application use less (as a percentage) of the CPU time is to make sure that, when you start it, the CPU is already working flat out (ie 100%) on other tasks. The o/s should then make sure that your starting application gets only a smaller share of CPU time.
And if that previous paragraph makes you shout 'that's not what I meant !' well, I only offer it as an example of how a single measurement of CPU time (or most other performance measures for that matter) is almost useless as the basis for an argument for refactoring or any other corrective action.

Related

Making IO application more CPU efficent

I have an application that takes files from one place and moves them to another place - pretty much all this application does is checks if files are in s3 and downloads ones that are not to another s3. Currently application uses very low amounts of provided CPU. From this post, my understanding that it is to be expected (seeing as my app is pretty much I/O and nothing more).
My initial idea was to lower the number of CPUs provided to the app. However, providing less and less negatively impacted the speed at which my app performs its duties (which according to this article kind of make sense - less CPU means less total clock speed). This is not an option as it needs to run somewhat fast.
I am using kafka messages to start my app. So another idea of mine was to increase the number of partitions in my topic from which my app consumes the messages (so that I can increase the no. of threads that can run concurrently). That allowed me to reduce the number of CPU that I provide to my app (while maintaining the desired processing speed) but my app still uses very low amounts of CPUs.
My app runs in kubernates whose cluster is deployed to EC2s, if that is of any difference. My app is springBoot java. I tried to only give it a minimum number of CPUs, while maxing out the no. of concurrent threads in my app, but again I can see a lot of wasted CPU there.
My question is then as follows: is it possible to somehow make an application to use all available CPU (thus making it more efficient) in this scenario? Is there a config or a method or something that does that? Or for an app that checks data is present and downloads data somewhere else, this is an expected behavior - increasing the number of available resource would improve speed at which my app runs but as a cons of that, there will be waster CPU? (so I am in the classic "good comes with the bad" sort of situation here?)

What methodology would you use to measure the load capacity of a software server application?

I have a high-performance software server application that is expected to get increased traffic in the next few months.
I was wondering what approach or methodology is good to use in order to gauge if the server still has the capacity to handle this increased load?
I think you're looking for Stress Testing and the scenario would be something like:
Create a load test simulating current real application usage
Start with current number of users and gradually increase the load until
you reach the "increased traffic" amount
or errors start occurring
or you start observing performance degradation
whatever comes the first
Depending on the outcome you either can state that your server can handle the increased load without any issues or you will come up with the saturation point and the first bottleneck
You might also want to execute a Soak Test - leave the system under high prolonged load for several hours or days, this way you can detect memory leaks or other capacity problems.
More information: Why ‘Normal’ Load Testing Isn’t Enough
Test the product with one-tenth the data and traffic. Be sure the activity is 'realistic'.
Then consider what will happen as traffic grows -- with the RAM, disk, cpu, network, etc, grow linearly or not?
While you are doing that, look for "hot spots". Optimize them.
Will you be using web pages? Databases? Etc. Each of these things scales differently. (In other words, you have not provided enough details in your question.)
Most canned benchmarks focus on one small aspect of computing; applying the results to a specific application is iffy.
I would start by collecting base line data on critical resources - typically, CPU, memory usage, disk usage, network usage - and track them over time. If any of those resources show regular spikes where they remain at 100% capacity for more than a fraction of a second, under current usage, you have a bottleneck somewhere. In this case, you cannot accept additional load without likely outages.
Next, I'd start figuring out what the bottleneck resource for your application is - it varies between applications, but in most cases it's the bottleneck resource that stops you from scaling further. Your CPU might be almost idle, but you're thrashing the disk I/O, for instance. That's a tricky process - load and stress testing are the way to go.
If you can resolve the bottleneck by buying better hardware, do so - it's much cheaper than rewriting the software. If you can't buy better hardware, look at load balancing. If you can't load balance, you've got to look at application architecture and implementation and see if there are ways to move the bottleneck.
It's quite typical for the bottleneck to move from one resource to the next - you've got CPU to behave, but now when you increase traffic, you're spiking disk I/O; once you resolve that, you may get another CPU challenge.

high load low cpu low iowait, why?

Look at the those peaks in the first graph, which factor can cause this?
cpu 24X6
There's a lot of stuff going on in any general purpose computer. When I performance profiled apps in a former life, I saw this all the time and factored it out.
It's caused by a whole host of sources: Processor dealing with interrupts, some disk maintenance routine, file system clean up, completely useless background apps that have been installed unknown to you as automatically launched services, etc.
Your plot of idle time is a little disconcerting. It is awfully low. What apps do you have running taking up all that processing? Also, if your memory is low, say because you have 20 or 30 browser tabs/windows open, your CPU load will go through the roof due to all that page and context swapping.

How to reduce time taken for large calculations in MATLAB

When using the desktop PC's in my university (Which have 4Gb of ram), calculations in Matlab are fairly speedy, but on my laptop (Which also has 4Gb of ram), the exact same calculations take ages. My laptop is much more modern so I assume it also has a similar clock speed to the desktops.
For example, I have written a program that calculates the solid angle subtended by 50 disks at 500 points. On the desktop PC's this calculation takes about 15 seconds, on my laptop it takes about 5 minutes.
Is there a way to reduce the time taken to perform these calculations? e.g, can I allocate more ram to MATLAB, or can I boot up my PC in a way that optimises it for using MATLAB? I'm thinking that if the processor on my laptop is also doing calculations to run other programs this will slow down the MATLAB calculations. I've closed all other applications, but I know theres probably a lot of stuff going on I can't see. Can I boot my laptop up in a way that will have less of these things going on in the background?
I can't modify the code to make it more efficient.
Thanks!
You might run some of my benchmarks which, along with example results, can be found via:
http://www.roylongbottom.org.uk/
The CPU core used at a particular point in time, is the same on Pentiums, Celerons, Core 2s, Xeons and others. Only differences are L2/L3 cache sizes and external memory bus speeds. So you can compare most results with similar vintage 2 GHz CPUs. Things to try, besides simple number crunching tests.
1 - Try memory test, such as my BusSpeed, to show that caches are being used and RAM not dead slow.
2 - Assuming Windows, check that the offending program is the one using most CPU time in Task Manager, also that with the program not running, that CPU utilisation is around zero.
3 - Check that CPU temperature is not too high, like with SpeedFan (free D/L).
4 - If disk light is flashing, too much RAM might be being used, with some being swapped in and out. Task Manager Performance would show this. Increasing RAM demands can be checked my some of my reliability tests.
There are many things that go into computing power besides RAM. You mention processor speed, but there is also number of cores, GPU capability and more. Programs like MATLAB are designed to take advantage of features like parallelism.
Summary: You can't compare only RAM between two machines and expect to know how they will perform with respect to one another.
Side note: 4 GB is not very much RAM for a modern laptop.
Firstly you should perform a CPU performance benchmark on both computers.
Modern operating systems usually apply the most aggressive power management schemes when it is run on laptop. This usually means turning off one or more cores, or setting them to a very low frequency. For example, a Quad-core CPU that normally runs at 2.0 GHz could be throttled down to 700 MHz on one CPU while the other three are basically put to sleep, while it is on battery. (Remark. Numbers are not taken from a real example.)
The OS manages the CPU frequency in a dynamic way, tweaking it on the order of seconds. You will need a software monitoring tool that actually asks for the CPU frequency every second (without doing busy work itself) in order to know if this is the case.
Plugging in the laptop will make the OS use a less aggressive power management scheme.
(If this is found to be unrelated to MATLAB, please "flag" this post and ask moderator to move this question to the SuperUser site.)

Optimal CPU utilization thresholds

I have built software that I deploy on Windows 2003 server. The software runs as a service continuously and it's the only application on the Windows box of importance to me. Part of the time, it's retrieving data from the Internet, and part of the time it's doing some computations on that data. It's multi-threaded -- I use thread pools of roughly 4-20 threads.
I won't bore you with all those details, but suffice it to say that as I enable more threads in the pool, more concurrent work occurs, and CPU use rises. (as does demand for other resources, like bandwidth, although that's of no concern to me -- I have plenty)
My question is this: should I simply try to max out the CPU to get the best bang for my buck? Intuitively, I don't think it makes sense to run at 100% CPU; even 95% CPU seems high, almost like I'm not giving the OS much space to do what it needs to do. I don't know the right way to identify best balance. I guessing I could measure and measure and probably find that the best throughput is achived at a CPU avg utilization of 90% or 91%, etc. but...
I'm just wondering if there's a good rule of thumb about this??? I don't want to assume that my testing will take into account all kinds of variations of workloads. I'd rather play it a bit safe, but not too safe (or else I'm underusing my hardware).
What do you recommend? What is a smart, performance minded rule of utilization for a multi-threaded, mixed load (some I/O, some CPU) application on Windows?
Yep, I'd suggest 100% is thrashing so wouldn't want to see processes running like that all the time. I've always aimed for 80% to get a balance between utilization and room for spikes / ad-hoc processes.
An approach i've used in the past is to crank up the pool size slowly and measure the impact (both on CPU and on other constraints such as IO), you never know, you might find that suddenly IO becomes the bottleneck.
CPU utilization shouldn't matter in this i/o intensive workload, you care about throughput, so try using a hill climbing approach and basically try programmatically injecting / removing worker threads and track completion progress...
If you add a thread and it helps, add another one. If you try a thread and it hurts remove it.
Eventually this will stabilize.
If this is a .NET based app, hill climbing was added to the .NET 4 threadpool.
UPDATE:
hill climbing is a control theory based approach to maximizing throughput, you can call it trial and error if you want, but it is a sound approach. In general, there isn't a good 'rule of thumb' to follow here because the overheads and latencies vary so much, it's not really possible to generalize. The focus should be on throughput & task / thread completion, not CPU utilization. For example, it's pretty easy to peg the cores pretty easily with coarse or fine-grained synchronization but not actually make a difference in throughput.
Also regarding .NET 4, if you can reframe your problem as a Parallel.For or Parallel.ForEach then the threadpool will adjust number of threads to maximize throughput so you don't have to worry about this.
-Rick
Assuming nothing else of importance but the OS runs on the machine:
And your load is constant, you should aim at 100% CPU utilization, everything else is a waste of CPU. Remember the OS handles the threads so it is indeed able to run, it's hard to starve the OS with a well behaved program.
But if your load is variable and you expect peaks you should take in consideration, I'd say 80% CPU is a good threshold to use, unless you know exactly how will that load vary and how much CPU it will demand, in which case you can aim for the exact number.
If you simply give your threads a low priority, the OS will do the rest, and take cycles as it needs to do work. Server 2003 (and most Server OSes) are very good at this, no need to try and manage it yourself.
I have also used 80% as a general rule-of-thumb for target CPU utilization. As some others have mentioned, this leaves some headroom for sporadic spikes in activity and will help avoid thrashing on the CPU.
Here is a little (older but still relevant) advice from the Weblogic crew on this issue: http://docs.oracle.com/cd/E13222_01/wls/docs92/perform/basics.html#wp1132942
If you feel your load is very even and predictable you could push that target a little higher, but unless your user base is exceptionally tolerant of periodic slow responses and your project budget is incredibly tight, I'd recommend adding more resources to your system (adding a CPU, using a CPU with more cores, etc.) over making a risky move to try to squeeze out another 10% CPU utilization out of your existing platform.

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