HP-UX Encrypted Volume and File System Performance and Tuning

4
EVFS Processor Affinity
EVFS is CPU intensive. The EVFS pseudo-driver is kernel-resident, and all encrypted data must be
encrypted by CPU before being written to the storage device or decrypted after being read from the
storage device. A critical measure of performance for EVFS is what level of CPU utilization is
required to read/write a given measure of data throughput.
EVFS is multi-threaded. The number of system threads running EVFS is configurable. The default
thread configuration is the number of system processors minus 1 (EVFS threads = processors – 1).
Empirical testing has shown that the default configuration is most effective for maximizing EVFS
performance. However, some environments require the flexibility of configuring EVFS threads on
specific processors, so the option of running EVFS at less than optimal performance is available if
required.
EVFS thread configuration is administered when EVFS is started with the evfsadm command: evfsadm
start [–n number]. EVFS starts a father process named evfsevold. The father process manages the
processor threads. In the figure below, the HP-UX system has 8 processors, and the evfsevold process
shows 8 threads – 1 for the father plus the 7 processor threads.
Figure 2 - EVFS father process
The 7 processor threads are shown below.