shmseg(5) [hpux man page]
shmseg(5) File Formats Manual shmseg(5) NAME
shmseg - maximum number of System V shared memory segments per process VALUES
Default Allowed values Maximum: Any value less than or equal to DESCRIPTION
Shared memory is an efficient InterProcess Communications (IPC) mechanism. One process creates a shared memory segment and attaches it to its address space. Any processes looking to communicate with this process through the shared memory segment then attach the shared memory segment to their corresponding address spaces. Once attached, a process can read from or write to the segment depending on the permissions specified while attaching it. This tunable sets an upper limit to the number of segments which can be attached per process. Who is Expected to Change This Tunable? Anyone. Restrictions on Changing Changes to this tunable take effect immediately. When Should the Value of This Tunable Be Raised? If user processes reach their limit, more segments are desired, and the current value is less than the total number of segments in the sys- tem What Are the Side Effects of Raising the Value? A single process will be able to acquire more segments, possibly starving another process which previously was able to acquire all the seg- ments it needed. In this case, should be raised if it is below it's maximum. When Should the Value of This Tunable Be Lowered? This tunable should only be lowered to enforce segment policy on user processes, or if one runaway process is hogging the global-segment pool. Otherwise, keeping the maximum higher than the common usage is harmless. What Are the Side Effects of Lowering the Value? None. What Other Tunable Values Should Be Changed at the Same Time? should be considered, as previously described. WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its meaning changed in future releases of HP-UX. Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parameter values. After installation, some tunable parameters may no longer be at the default or recommended values. For information about the effects of installation on tun- able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see at AUTHOR
was developed by HP. SEE ALSO
shmmni(5). Tunable Kernel Parameters shmseg(5)
Check Out this Related Man Page
max_mem_window(5) File Formats Manual max_mem_window(5) NAME
max_mem_window - maximum number of group-private 32-bit shared memory configurable by users VALUES
Default Allowed values DESCRIPTION
Processes in a PA-RISC 32-bit architecture usually share the global quadrants 3 and 4 for such things as I/O mappings, shared libraries, shared mapped files, and so on. However, you may wish to use quadrant 3 in a more limited sharing fashion with only a select group of pro- cesses. Memory windows allow this functionality. If this tunable is set to 32-bit programs always use the global Q3 and Q4 for shared memory. If this tunable is greater than processes in defined groups use a Q3 private to that group, and then the globally shared Q4 if Q3 is full. Who is Expected to Change This Tunable? Anyone. Restrictions on Changing Changes to this tunable take effect immediately. When Should the Value of This Tunable Be Raised? This tunable should be raised if more group-private Q3 areas are needed by the users of the system. Each memory window in active use will require approximately 1Mb of kernel memory. Windows no longer in use will have this memory reclaimed by the system as is feasible. What Are the Side Effects of Raising the Value? A little more memory is used in the kernel. When Should the Value of This Tunable Be Lowered? If process groups are not being used, or not being used in the quantity set by the tunable, there is really no point to having this value higher than what is actually needed. What Are the Side Effects of Lowering the Value? The kernel uses a little less memory. If the value is set to no group-private Q3's are allowed. What Other Tunable Values Should Be Changed at the Same Time? None. WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its meaning changed in future releases of HP-UX. Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parameter values. After installation, some tunable parameters may no longer be at the default or recommended values. For information about the effects of installation on tun- able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see at AUTHOR
was developed by HP. SEE ALSO
getmemwindow(1M), setmemwindow(1M), services.window(4). Tunable Kernel Parameters max_mem_window(5)