Category: Windows threads

Windows threads

A process contains its own independent virtual address space with both code and data, protected from other processes. Each process, in turn, contains one or more independently executing threads.

A thread running within a process can create new threads, create new independent processes, and manage communication and synchronization between the objects. By creating and managing processes, applications can have multiple, concurrent tasks processing files, performing computations, or communicating with other networked systems. It is even possible to exploit multiple processors to speed processing.

This chapter explains the basics of process management and also introduces the basic synchronization operations that will be used throughout the rest of the book. Every process contains one or more threads, and the Windows thread is the basic executable unit.

windows threads

Threads are scheduled on the basis of the usual factors: availability of resources such as CPUs and physical memory, priority, fairness, and so on. Windows has supported symmetric multiprocessing SMP since NT4, so threads can be allocated to separate processors within a system.

Windows Threads

From the programmer's perspective, each Windows process includes resources such as the following components:. A virtual address space that is distinct from other processes' address spaces, except where memory is explicitly shared. Note that shared memory-mapped files share physical memory, but the sharing processes will use different virtual addresses to access the mapped file. Each thread in a process shares code, global variables, environment strings, and resources. Each thread is independently scheduled, and a thread has the following elements:.

Figure shows a process with several threads. This figure is schematic and does not indicate actual memory addresses, nor is it drawn to scale. Figure A Process and Its Threads. This chapter shows how to work with processes consisting of a single thread.

Chapter 7 shows how to use multiple threads. Note : Figure is a high-level overview from the programmer's perspective. There are numerous technical and implementation details, and interested readers can find out more in Inside Windows Solomon and Russinovich. Stevens does not discuss threads; everything is done with processes. Needless to say, vendors and others have provided various thread implementations for many years; they are not a new concept.

Creating Threads

Pthreads is, however, the most widely used standard, and proprietary implementations are obsolete. See All Related Store Items.

Hart Feb 18, This chapter explains the basics of process management and also introduces basic synchronization operations. If you're at all interested in Windows system programming, this is the place to start. This chapter is from the book. Related Resources Store Articles. Join Sign In. All rights reserved.The Microsoft Press Store by Pearson.

Where relevant performance counters or kernel variables exist, they are mentioned. Because processes and threads touch so many components in Windows, a number of terms and data structures such as working sets, objects and handles, system memory heaps, and so on are referred to in this chapter but are explained in detail elsewhere in the book. To fully understand this chapter, you need to be familiar with the terms and concepts explained in Chapter 1 and Chapter 2, such as the difference between a process and a thread, the Windows virtual address space layout, and the difference between user mode and kernel mode.

This section describes the key Windows process data structures. Also listed are key kernel variables, performance counters, and functions and tools that relate to processes.

Thread data structures are explained in the section Thread Internals later in this chapter. The EPROCESS block and its related data structures exist in system address space, with the exception of the process environment block PEBwhich exists in the process address space because it contains information that needs to be accessed by user-mode code.

Finally, the kernel-mode part of the Windows subsystem Win32k. Figure is a simplified diagram of the process and thread data structures. Each data structure shown in the figure is described in detail in this chapter. See Chapter 1 for more information on the kernel debugger and how to perform kernel debugging on the local system. The output truncated for the sake of space on a bit system looks like this:.

The dt command shows the format of a process block, not its contents. An annotated example of the output from this command is included later in this chapter.

Table explains some of the fields in the preceding experiment in more detail and includes references to other places in the book where you can find more information about them.

Processes and Threads

Common dispatcher object header, pointer to the process page directory, list of kernel thread KTHREAD blocks belonging to the process, default base priority, affinity mask, and total kernel and user time and CPU clock cycles for the threads in the process. Unique process ID, creating process ID, name of image being run, window station process is running on. Limits on processor usage, nonpaged pool, paged pool, and page file usage plus current and peak process nonpaged and paged pool usage.

Note: Several processes can share this structure: all the system processes in session 0 point to a single systemwide quota block; all other processes in interactive sessions share a single quota block.

Series of data structures that describes the status of the portions of the address space that exist in the process.To write highly responsive and scalable applications, you must avail the power of multi threading programming. While working on. In this article, I would like to share some of the basics about Windows thread which may help you in understanding how operating system implements threads. There are three basic components of Windows thread:. All of these three components together create Windows thread.

I tried to explain all of them one by one below but before looking into these three components, let's have a brief introduction about Windows kernel and kernel objects as these are the most important part of Windows operating system. Kernel is the main component of any operating system.

It is a bridge between applications and hardware. Kernel provides layer of abstraction through which application can interact with hardware. Kernel is the part of the operating system that loads first, and it remains in physical memory. The kernel's primary function is to manage the computer's hardware and resources and allow other programs to run and use these resources.

To know more about kernel, visit this link. Kernel needs to maintain lots of data about numerous resources such as processes, threads, files, etc. Each kernel object is simply a memory block allocated by the kernel and is accessible only to the kernel.

This memory block is a data structure whose members maintain information about the object. Some members security descriptor, usage count, and so on are same across all object types, but most data members are specific to the type of kernel object.

If you are curious to see the list of all the kernel object types, then you can use free WinObj tool from Sysinternals located here. First and very basic component of Windows thread is thread kernel object. For every thread in system, operating system create one thread kernel object. Operating systems use these thread kernel objects for managing and executing threads across the system.An application consists of one or more processes.

A processin the simplest terms, is an executing program. One or more threads run in the context of the process. A thread is the basic unit to which the operating system allocates processor time.

windows threads

A thread can execute any part of the process code, including parts currently being executed by another thread. A job object allows groups of processes to be managed as a unit. Job objects are namable, securable, sharable objects that control attributes of the processes associated with them. Operations performed on the job object affect all processes associated with the job object.

A thread pool is a collection of worker threads that efficiently execute asynchronous callbacks on behalf of the application.

The thread pool is primarily used to reduce the number of application threads and provide management of the worker threads. A fiber is a unit of execution that must be manually scheduled by the application.

Fibers run in the context of the threads that schedule them. User-mode scheduling UMS is a lightweight mechanism that applications can use to schedule their own threads. UMS threads differ from fibers in that each UMS thread has its own thread context instead of sharing the thread context of a single thread.

Skip to main content. Exit focus mode. Yes No. Any additional feedback? Skip Submit. Is this page helpful?This is the fourth post in my Pushing the Limits of Windows series that explores the boundaries of fundamental resources in Windows. Process and threads, for example, require physical memory, virtual memory, and pool memory, so the number of processes or threads that can be created on a given Windows system is ultimately determined by one of these resources, depending on the way that the processes or threads are created and which constraint is hit first.

While they can stand on their own, they assume that you read them in order.

POSIX Threads for Windows

Pushing the Limits of Windows: Physical Memory. Pushing the Limits of Windows: Virtual Memory. Pushing the Limits of Windows: Processes and Threads.

Pushing the Limits of Windows: Handles. A Windows process is essentially container that hosts the execution of an executable image file.

Processes operate with a security context, called a token, that identifies the user account, account groups, and privileges assigned to the process. Besides basic information about a thread, including its CPU register state, scheduling priority, and resource usage accounting, every thread has a portion of the process address space assigned to it, called a stack, which the thread can use as scratch storage as it executes program code to pass function parameters, maintain local variables, and save function return addresses.

Because stacks grow downward in memory, the system places guard pages beyond the committed part of the stack that trigger an automatic commitment of additional memory called a stack expansion when accessed. The linker defaults to a reserve of 1MB and commit of one page 4Kbut developers can override these values either by changing the PE values when they link their program or for an individual thread in a call to CreateThread.

You can use a tool like Dumpbin that comes with Visual Studio to look at the settings for an executable. Even if the thread had no code or data and the entire address space could be used for stacks, a bit process with the default 2GB address space could create at most 2, threads.

Again, since part of the address space was already used by the code and initial heap, not all of the 2GB was available for thread stacks, thus the total threads created could not quite reach the theoretical limit of 2, The reason for the discrepancy comes from the fact that when you run a bit application on bit Windows, it is actually a bit process that executes bit code on behalf of the bit threads, and therefore there is a bit thread stack and a bit thread stack area reserved for each thread.

I got different results when I ran bit Testlimit on bit Windows 7, however:. Randomization of DLL loading, thread stack and heap placement, helps defend against malware code injection. As I mentioned, a developer can override the default stack reserve. Testlimit sets the default stack reservation in its PE image to 64K and when you include the —n switch along with the —t switch, Testlimit creates threads with 64K stacks.

Resident available memory is the physical memory that can be assigned to data or code that must be kept in RAM. A basic kernel stack is 12K on bit Windows and 24K on bit Windows. Once the resident available memory limit is hit, many basic operations begin failing. Resident available memory is obviously still a potential limiter, though. The bit version of Testlimit Testlimit Once the commit level reached the size of RAM, the rate of thread creation slowed to a crawl because the system started thrashing, paging out stacks of threads created earlier to make room for the stacks of new threads, and the paging file had to expand.

The results are the same when the —n switch is specified, because the threads have the same initial stack commitment. The number of processes that Windows supports obviously must be less than the number of threads, since each process has one thread and a process itself causes additional resource usage. If the only cost of a process with respect to resident available memory was the kernel-mode thread stack, Testlimit would have been able to create far more than 8, threads on a 2GB system.

Dividing the amount of resident memory Testlimit used 1. Since a bit kernel stack is 24K, that leaves about K unaccounted for. This acts as a guarantee to the process that no matter what, there will enough physical memory available to hold enough data to satisfy its minimum working set. The remaining roughly 6K is resident available memory charged for additional non-pageable memory allocated to represent a process. A process on bit Windows will use slightly less resident memory because its kernel-mode thread stack is smaller.

As they can for user-mode thread stacks, processes can override their default working set size with the SetProcessWorkingSetSize function. Testlimit supports a —n switch, that when combined with —p, causes child processes of the main Testlimit process to set their working set to the minimum possible, which is 80K.

windows threads

Testlimit executed with the —n switch on a Windows 7 system with 4GB of RAM hit a limit other than resident available memory: the system commit limit:. Here you can see the kernel debugger reporting not only that the system commit limit had been hit, but that there have been thousands of memory allocation failures, both virtual and paged pool allocations, following the exhaustion of the commit limit the system commit limit was actually hit several times as the paging file was filled and then grown to raise the limit :.

The baseline commitment before Testlimit ran was about 1. The initial thread stack commitment, described earlier, has a negligible impact with the rest coming from the memory required for the process address space data structures, page table entries, the handle table, process and thread objects, and private data the process creates when it initializes.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. The basic idea is you call CreateThread and pass it a pointer to your thread function, which is what will be run on the target thread once it is created. You also have the option of calling SHCreateThread —same basic idea but will do some shell-type initialization for you if you ask it, such as initializing COM, etc.

You would use the CreateThread function. You mentioned semaphores as well. For that you would use CreateSemaphore. Learn more. Using threads in C on Windows. Simple Example? Asked 10 years, 3 months ago. Active 4 years, 3 months ago.

Viewed 49k times. Could you please give me a simple code example? Jiminion 4, 1 1 gold badge 19 19 silver badges 47 47 bronze badges. While this may be a simple RTFM question, it isn't not a real question. After all, there are several real answers already. Active Oldest Votes. This will be the first function called on the new thread. See MSDN for more details. Keep in mind, however, that if you're going to use the CRT in the new thread you may need to be extremely careful.

I think that also in other CRTs it should go somehow like that. Would this work for C as well? Win32 is a C api, so, yes, it should work.

Atomic operations and mutexes are good. I use CreateThread etc, not pthreads.

Windows Processes and Threads: Weaving It All Together

Is pthreads avail. You may be able to use mingw and cygwin however. The Overflow Blog.Keep in touch and stay productive with Teams and Officeeven when you're working remotely. Learn how to collaborate with Office Tech support scams are an industry-wide issue where scammers trick you into paying for unnecessary technical support services. You can help protect yourself from scammers by verifying that the contact is a Microsoft Agent or Microsoft Employee and that the phone number is an official Microsoft global customer service number.

With Intel i9 and AMD Threadripper CPUs featuring more than 28 threads of execution, Windows 10 appears to be preventing the use of all available hardware resources with professional-grade Digital Audio Workstation software, such as Cubase.

Besides Steinberg's proposed options, i. Thank you. This thread is locked. You can follow the question or vote as helpful, but you cannot reply to this thread. Did this solve your problem? Yes No. Sorry this didn't help. Rohn, all versions of Windows 10 appear to be affected and, unfortunately, your response is completely off topic.

You may find useful to read Steinberg's article more carefully. I use Windows 10 for Workstations but it doesn't make any difference with regards to the limitation identified by Steinberg. Additionally, they have access to a registry work-around that we provided to them last year.

windows threads

They are able to share this with their customers as-needed. It's not something we share publicly because there are system-wide performance implications to just picking a random large number for the process cap. My only big question iswhat will be the future of DAW like Cubase to deal with the issue. Cross finger. ImagineMultisHeavy sampling stuffsall those. I am considering in final decision to downgrade to win 8. Unlikelysuch a wasting effort to buy 10 - 14 coreI 9giving an unsatisfactory audio performance.

Like I mention above, Steinberg have access to both our recommended practices as well as an interim workaround that doesn't limit your cores or in any way cut down performance for DAW use.

Their support should be willing to provide you with the value appropriate to your software and system setup. You actually spoke to Steinberg support on the phone and they didn't have the workaround for you? I follow the suggestion to add Audio engine. I do MMCSS-test and everytime come up with priority 32 and 96 failed out of thread, no change before and after follow Steinberg procedure. AFAIK, there is no need to limit the to That audioengine. Similarly, you don't need to downgrade to 8.

If you speak to Steinberg directly, through their support, they should be able to calculate the right number for your PC and software and give you the registry entry to set a more appropriate MMCSS cap.

Wake up Steinberg and be aware of customers issue.

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