HP-UX Processor Sets

HP-UX Processor Sets 15
Default Pset. When the last processor from a processor set is reassigned to another
processor set, all applications in the now-to-be-empty processor set are migrated to
the Default Pset.
System Daemon Processes
The HP-UX operating system provides a set of kernel-private daemon processes to perform
system-level activities and services. Users may configure processor sets in such a way that
only a minimum number of processors are left in the Default Pset. If kernel daemon processes
were to be restricted to the Default Pset, they may get starved. Therefore, since system
responsiveness and the progress of user applications depend on these daemon processes
running regularly as needed, HP-UX Processor Sets do not restrict the kernel daemons to
processor set boundaries. Instead, HP-UX has introduced the concept of the Kernel Pset for
these daemon processes.
(Note: These daemon processes do not include the user space
daemon processes.)
The key features of the Kernel Pset are as follows:
ÿ All processors in the system are by default assigned to the Kernel Pset. Kernel
daemon processes and threads may run on any processors in the Kernel Pset.
ÿ Processors in the Default Pset are always available to the Kernel Pset.
Since user daemon processes are assigned by default to the Default Pset, the administrator
should assign sufficient processor resources to the Default Pset to ensure that those user
daemons critical to system responsiveness do not get starved. Some examples of user-space
daemons that can have impact on the overall system responsiveness and throughput are as
follows:
ÿ If the system is configured with remote file systems using NFS (Network File
System), the responsiveness of NFS daemons is critical to performance of
applications that access these remote file systems.
ÿ For server systems that have a large number of remote users who access the system
through remote logins, the responsiveness of inetd and rlogind daemons is
important to provide smooth and quick access to remote users.
Alternately, the administrator can create a new processor set dedicated for these critical user
daemons and then allocate sufficient processor resources to ensure overall system progress.
User Interfaces
To programmatically manage system processor set configuration and workload assignment,
HP-UX Processor Sets support the following application programming interfaces (APIs) for
applications: