I built a windows service that spawn child process , i noticed that after 100 childs process creation , i get failed to create new process, no error , just return immediately right after creation.
i am waiting on each process handle.
when i run the service from console , all work fine.
when i set my service to interact with desktop , seems to be fine.
from google search i found those article who helps me at least to increase the number of processes .
child process limits in service context and conhost.exe
How to increase the maximum number of child processes that can be spawned by a windows service — desktop heap limits
i used in my case DETACHED_PROCESS as a parameter to CreateProcess api , and i managed to increase from 100 to about 300 childs.
bSuccess = CreateProcess(NULL,
(LPSTR)(LPCTSTR)commandLine , // command line
NULL, // process security attributes
NULL, // primary thread security attributes
TRUE, // handles are inherited
DETACHED_PROCESS, // creation flags
NULL, // use parent's environment
NULL, // use parent's current directory
&siStartInfo, // STARTUPINFO pointer
&piProcInfo); // receives PROCESS_INFORMATION
still need to check how to increase the desktop heap ...
i found this solution at
How to increase the maximum number of child processes that can be spawned by a windows service — desktop heap limits
WARNING: this affects the desktop heap of all services! Do not make it larger than necessary or you will push the system to consume more resource and you may bump up against problems in the total available desktop heap size.
If you find that you cannot open more than about 100 total projects, even on a very large RAM server, you may have run into a limit of the Windows "desktop heap size".
The problem is that service sessions under windows (where the services run) have less of this "desktop heap" space available for creating windows.
The short version is:
Services get smaller desktop heaps than interactive sessions.
Desktop heap size limits the number of windows
Each sub-server creates one or more “windows” even if we can’t see them.
Solution:
Backup your registry before making any changes!
Run regedit.exe as administrator
Edit the registry value:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\SubSystems\Windows
You will see a string like:
%SystemRoot%\system32\csrss.exe ObjectDirectory=\Windows SharedSection=1024,20480,768 Windows=On SubSystemType=Windows ServerDll=basesrv,1 ServerDll=winsrv:UserServerDllInitialization,3 ServerDll=winsrv:ConServerDllInitialization,2 ServerDll=sxssrv,4 ProfileControl=Off MaxRequestThreads=16
The critical bit is:
SharedSection=1024,20480,768
The second number (20480) is the size for interactive sessions. The third number (768) is the size of non-interactive (services) sessions. Note how the third number is 26x smaller than the second. Experimentally, we found that changing this to:
SharedSection=1024,20480,2048
Increased the project limit from 106 to 270, almost perfectly scaling with the heap size. Pick a value that reflects the maximum number of projects that you expect to be opened simultaneously by all users on the system. Do not make this value larger than necessary, and no larger than 8192, as each service in your system will consume more of a precious resource.
good luck
yaniv tzanany
