петък, 21 март 2008 г.
There are a lot of cases in which we as developers want to know how much free memory is there (or the state of some of the other system resources). This can be used for deciding whether we can handle another request, or is there enough memory (and CPU of course) to start some background work meanwhile. A lot of examples can be given about such situations.
Ok, but how we can answer this question in C#?
The approach which I will show is a very good start for diving in the topic of monitoring. What is the way to monitor the system resources in Windows? The answer is: Performance Counters. There are a lot of counters out there which can give a lot of data. Yes, there is no mistake – just pure data. Our task is to observe, collect, manipulate mathematically, etc. this data such that we can extract meaning from it i.e. to transform it in information. Keep in mind that “Performance Monitoring is a complex subject and in some ways more of an art than a science.”
Just for completeness I will add that you can check some of the available counters on your own system /they can differ depending on what have been installed/ from Control Panel ->Administrative Tools -> Performance. There – right click -> Add counter. The following box appears:
OK that’s enough knowledge for you to start observing some counter if you haven’t already in the past.
The counter which we are interested in today is connected with memory, so it should be in Memory performance object. The right counter is one of the following: Available Bytes, Available KBytes, Available MBytes.
"Available Bytes\KBytes\MBytes shows the amount of physical memory, in bytes\kilobytes\megabytes, available to processes running on the computer. It is calculated by adding the amount of space on the Zeroed, Free, and Standby memory lists. Free memory is ready for use; Zeroed memory consists of pages of memory filled with zeros to prevent subsequent processes from seeing data used by a previous process; Standby memory is memory that has been removed from a process' working set (its physical memory) on route to disk, but is still available to be recalled. This counter displays the last observed value only; it is not an average."
How to retrieve data from performance counters in C#? There is a namespace in .NET named System.Diagnostics . There are a bunch of classes which give us the power to play with these counters. It is very straight forward and easy. You can see the simplicity from my sample which is only 3-4 lines of code.
In this manner we can retrieve the free memory with C#.
There are a lot other useful counters out there in Windows such as these for the processor, disk usage, etc. Of course if you have installed .NET framework, there are a lot counters connected with the CLR as a whole.
In the future I am planning covering some of other performance counters and connected classes in .NET so stay turned. Hope this helps!