Is there a way to expand the current WorkingSet of a process to 1GB? [duplicate]

Question

Possible Duplicate:
Is there any way to force the WorkingSet of a process to be 1GB in C++?

We would like to increase the WorkingSet of a .NET process to 1GB, in advance, to avoid page faults.

Is there a way to do this in .NET?

Update

Unfortunately, it appears that even if we do a call to SetProcessWorkingSetSizeEx, the garbage collection trims the working set down anyway, bypassing MinWorkingSet (see "Automatic GC.Collect() in the diagram below).

In the picture below, is there a way to lock the process WorkingSet (the green line) to 1GB, to avoid the spike in page faults (the red lines) that occur when allocating new memory into the process?

The reason this would be awesome is that every time a page fault occurs, it blocks the thread for 250us, which hits application performance badly.

Update

Quote from: "Windows via C/C++, Fifth Edition, Jeffrey Richter (Wintellect)"

Calls to SetProcessWorkingSetSize by an individual process are ignored unless the process is just trying to empty its working set. To set this limit, specify the JOB_OBJECT_LIMIT_WORKINGSET flag in the LimitFlags member.

This book is implying that the only way to set the WorkingSet is by assigning the process to a Job Object and setting JOB_OBJECT_LIMIT_WORKINGSET and MinimumWorkingSetSize.

Update

SetProcessWorkingSetSizeEx has absolutely nothing to do with soft page faults. It only refers to hard page faults, as it prevents memory in the current WorkingSet being paged out to the hard drive.

Update

It turns out that the only method to increase the WorkingSet is to run .NET using an extremely specialized CLR Host written in C++ (see my answer below).

Answer 1

To achieve what you want you need to call/pinvoke SetWorkingSetSizeEx with 1 GB as minimum (second param) and QUOTA_LIMITS_HARDWS_MIN_ENABLE as fourth param which makes sure that workingset size won't go below minimum you gave even in "high memory pressure" conditions of the system.

The system behaviour also depends on privileges of the caller, depending on OS version etc. you might need SE_INC_WORKING_SET_NAME and/or SE_INC_BASE_PRIORITY_NAME !

Another (nicer) option which uses these APIs "behind the scenes" is a .NET wrapper you can find here.

Answer 2

If your problem was that your process was getting its WS trimmed too agressively in low-memory situations, you could take care of it by calling SetProcessWorkingSetSize or just setting Process.CurrentProcess.MinWorkingSet.

What you've shown, though, is that your working set is getting reduced by a GC. This tells me that what's really happening is the GC is deallocating the pages that make up your WS. If this is the case, you have an address space problem rather than a working set problem, and there's no system call you can make to prevent it. Ideally you would be able to tell the GC not to return its memory to the OS, but .NET doesn't have a feature like that.

To solve an address space problem you will have to reuse objects you have already allocated. If your problem is with the Large Object Heap, it's most likely due to collections. For example, rather than creating a new array/list/dictionary, call its Clear method and reuse it. If your problem is strings, you might be able to get away with using StringBuilders to stay out of the LOH.

If you have certain types of object you create lots of, consider creating a pool of them that get recycled. I've never done such a thing, but if I were to implement it I would create an object with a static factory method that pulls objects out of a pool and calls an initializer instead of having public constructors, and put a finalizer on it that puts it back in the pool and nulls out any references in it. Depending on the needs, the pool might be a ConcurrentBag<WeakReference<T>>.

Answer 3

I think assigning the process to a Job Object and setting JOB_OBJECT_LIMIT_WORKINGSET and MinimumWorkingSetSize might work.

Answer 4

The only way that we could find to increase the WorkingSet of a process under .NET, to reduce soft page faults, was to run the entire .NET application under a custom CLR Host. This is a non-trivial exercise, requiring about 800 lines of custom written, rather dense C++ code. The C++ code intercepts the .NET calls to the Win32 memory management methods, altering the behavior of the .NET runtime so it doesn't free memory as aggressively as it normally would.

This has the effect of incurring all of the soft page faults when the application starts up, so that during normal application execution, the number of soft page faults in the .NET app drops pretty much to zero.

This means that the application may be memory hungry, but it runs faster. In other words, we are sacrificing memory usage for increased realtime performance.