I just moved from WinXP to Win7.
My software needs to have real time response to I/O so it makes a busy-wait in one thread (which has affinity to run on one CPU).
The result is 100% CPU on one of the cores and 0% CPU for others, on Winows XP it worked just fine.
In Windows 7 the system freezes. (The software is a console application, for Windows application it behaves a bit different. only if the main thread make busy-wait without peeking messages it freezes)
Any ideas ?
So you're using a non real-time OS for realtime I/O. Simply put the code isn't working correctly and should do a non busy-wait (change to a sleep-wait) loop and change the thread timer settings to something that is realtime enough.
See this question to setup windows for millisecond precision on a timer callback.
How to trigger a C# function at a certain time with millisecond precision?
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I have a working application that needs to clear and setup very large buffers from time to time. Sometimes the operation takes longer than 5 seconds to complete and then Desktop Window Manager times out and declares the application to be hung.
Is there any technique to cause DWM to allow more time before this happens?
Delphi Seattle, Windows 10, 64-bit application
The right solution is to put the long running task in a thread so that it does not block your UI thread. You should do that.
If you cannot bring yourself to take that task one, and it can be quite tricky, you can always disable ghosting by calling DisableProcessWindowsGhosting. But you really ought not to do that. You really ought to put the work in a thread.
So, yesterday I opened task manager in Win 8 (64 bit) and noticed that Chrome (32-bit for some reason) didn't use the whole power my PC has got. So I was running an AI JavaScript program and I noticed that my CPU was running at 1% and Memory was only runnning 120 MB, and that forced me to think why would I wait 5 minutes for it to run instead of somehow boosting it to at least 60%. As far as I know Windows automatically distributes the hardware usage to programs so I'm asking what's the problem:
Is it because it's x32?
Is it because I should manually configure windows to give it more power?
Note: I did search Google, but all I got is that people actually complain about High CPU usage and I've got the opposite.
32 bit doesn't make a difference here. Javascript is inherently single-threaded, so by default (not counting web workers) it won't use more than a single core on your machine. It just cannot. Also memory usage doesn't necessarily tell you how hard a program is working. Some need lots of memory, others only little.
It's up to programs to use the resources of the machine most efficiently; if they don't, there is nothing you can do with Windows to make them run better or faster.
I've written a program that (among other things) downloads multiple large files from a server on the LAN, using TCP. This program runs fine under Linux, MacOS/X, and generally under Windows as well (it uses Qt for the GUI and straight sockets calls for networking), but on certain Windows machines the download appears to be too much for the machine to handle, and I'm wondering if anyone has any ideas as to why that is and what can be done about it.
When downloading files, my program spawns a separate I/O thread that basically just sits in a loop, downloading data over TCP and writing it to a file, writing 128KB per call to QFile:write(). Each file is typically several hundred megabytes long, and a typical download session writes out several dozen of these files. Note that the I/O thread runs independently of the GUI thread, so I wouldn't expect it to affect GUI's performance much if at all -- especially not when running on a multicore PC.
The PC in question is a Core-2Duo Quad Q6600 running at 2.40GHz, with 4GB of RAM. It's running Windows 7 Ultimate SP1, 32-bit. It is receiving data over a Gigabit Ethernet connection and writing it to files on the NTFS-formatted boot partition of the 232GB internal Hitachi ATA drive.
The symptom is that sometimes during a download (seemingly at random) the program's GUI will become non-responsive for 10 to 30 seconds at a time, and often the title bar of the window will have "(not responding)" appended to it. The symptom will then clear up again and the download will proceed normally again. Another symptom is that the desktop is extremely sluggish during the download... for example, if I click on the "Start" button, the Start menu will take ~30 seconds to populate, instead of being populated near-instantaneously as I would expect.
Note that Task Manager shows plenty of free memory, but it does show short spikes of CPU usage to 100% one one of the 4 cores, at the same time the problems are seen.
The data is arriving over Gigabit Ethernet, and if I have my program just receive the data and throw it away (without writing it to the hard drive), the machine can maintain a constant download rate of about 96MB/sec without breaking a sweat. If I write the received data to a file, however, the download rate decreases to about 37MB/sec, and the symptoms described above start to appear.
The interesting thing is that just for curiosity's sake I added this call to my I/O thread's entry function, just before the beginning of its event loop:
SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_BELOW_NORMAL);
When I did that, the "(not responding)" symptoms cleared, but then download speed was reduced to only ~25MB/sec.
So my questions are:
Does anyone know what might be causing the sporadic hangups of the GUI when the hard drive is under a heavy write-load?
Why does lowering the I/O thread's priority cause the download rate to drop so much, given that there are three idle cores on the machine? I would think that even a lower-priority thread would have plenty of CPU available in this situation.
Is there any way to get a maximum download rate without causing Windows' desktop responsiveness and/or my app's GUI responsiveness to suffer problems?
Without seeing any code is hard to answer but this seems to be something related to processors and the fact that your download thread is not leaving any space for other threads to performs other operations.
It seems it never waits and that the driver of the network card is not well written.
Are you sure your thread is entering in an idle state when there is no data incoming?
In OS with a single processor a for (;;) {} will consume 100% cpu and if it talks continuously with the kernel it may stops other processes or other threads for doing that, especially if there is a bug or a very bad behaviour in some network card driver in your case.
Probably putting the thread priority below normal you are asking the OS to use your thread less often, this gives by a magical combination of things that allow things to not hang too much.
Check the code, maybe you are forgetting something?
Check if adding a sleep(0) to force the OS to yield to another thread sometime will make things better, but this is a temporary fix, you should find why your thread is consuming 100% cpu, if it is.
My program is a slideshow. It runs on a machine with other processes, so while it's waiting to display the next slide I call SleepEx(N, false), expecting it to reduce to near-zero the amount of CPU it uses (N is between 100ms and 5000ms). On my development XP Pro machine that's exactly what happens but on my customer's XP Home machine it registers 30-80% CPU during the SleepEx(). The code is a single thread so whatever is using all that cpu is within the call to SleepEX(). Has anyone seen this before?
Which process is taking all that CPU? If you break into the process with a debugger - where in the stack trace is it spending time?
Try to use ProcDump to create a dump of the process when it reaches that CPU spike. Then analyze the stack trace to see where it's stuck. Do this several times you get a good sampling of where it's spending time.
I have seen this before. You block main window message processing thread.
You should not place Sleep() function in single-threaded application if it has main window message processing function. Windowed application always should process window messages without noticeable delay, in another case it will cause deadlock at least for application.
Consequences depends on windows platform, compiler settings and CPU configuration, usually application in debug mode has temporary workaround. But if you start such application compiled with release settings it can consume one CPU core with function, which have blocked his main window message processing thread.
Remarks section at MSDN Sleep() function description clearly states this situation.
You just have to lauch new thread, to use Sleep() function right there to allow free flow of window messages in main thread.
I'm running an application right now which seems to be running at full throttle, but even though the fan seems to be spinning at it's max and the activity monitor reports that the application is using 100% of the processor, I'm suspecting that at the most it is using 100% only of a single of the two cores on my machine.
How can I tell OS X to allow an application use 100%, or as much as the OS can allow, of the processing power of my computer? I have tried some terminal commands like "nice" and "renice" to set up the priority of this process but still can't get it to run at full throttle.
I also would like to know how to do the opposite, set a limit of the processor usage of an app, example set app X to run at 20%.
Is this possible to do without modifying the code of the app?
The answer to this depends upon whether your application is multi-threaded or not. If this is a single-threaded application, which it is unless you have specifically made it multi-threaded then the process will run on one core of your multi-core hardware. There is nothing you can do about this it's a function of the underlying operating system.
If your program is multi-threaded then it is possible to have different threads executing on separate cores. This will increase the overall usage of the process and allow figures greater than 100%.
You can not however force the machine to use 'all' of the processing power available, but you can influence it with nice.
In order to reduce the amount of processor used then you can use nice to lower the priority of the process. If you are root you can also use nice to increase the priority of your process