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HP-UX Reference > Mmax_async_ports(5)Tunable Kernel ParametersHP-UX 11i Version 2: December 2007 Update |
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NAMEmax_async_ports — maximum number of asynchronous disk ports that can be open at any time DESCRIPTIONThe asynchronous disk driver provides an interface to execute high-performance I/O to the raw disk. Instead of reading or writing directly to the raw disk, a process writes requests to the asynchronous driver which then makes appropriate calls to the disk driver. Every process that opens the asynchronous disk driver is assigned a port. The driver uses the port to keep track of I/O and other internal resources for that process. The number of opens to the asynchronous disk driver is limited by the number of available ports. The value of this tunable should not be set greater than the value of nproc since such a value cannot not be used. When Should the Value of This Tunable Be Raised?When the number of processes opening the driver needs to be more than the current value of the tunable. What Are the Side Effects of Raising the Value of This Tunable?The resources for the port are allocated from the kernel memory. Setting a higher value would result in the driver using more kernel memory. Other kernel components which may need kernel memory could suffer. When Should the Value of This Tunable Be Lowered?When the system is low on physical memory and there are not as many opens necessary to access the driver. WARNINGSAll 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 tunable values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see HP-UX Release Notes at http://docs.hp.com. |
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