Performance Tuning Siebel Software on the Sun Platform

7.6.4 Solaris MPSS <strong>Tuning</strong> for Oracle Server
Available as a standard feature since Solaris 9 OS, Multiple Page Size Support (MPSS)
allows a program to use any hardware-supported page sizes to access portions of virtual
memory. MPSS improves virtual memory performance by allowing applications to use
large page sizes, therefore improving resource efficiency and reducing overhead, and
accomplishes this without recompiling or recoding applications.
Enable MPSS (Multiple Page Size Support) for Oracle Server and shadow processes on
Solaris 9 OS or later versions to reduce the TLB miss% rate. It is recommended to use
the largest available page size if the TLB miss% is high.
Enabling MPSS for Oracle Processes
1. Enable the kernel cage if the machine is not an E10K or F15K, and reboot the
system. Kernel cage an be enabled by the following setting in /etc/system:
set kernel_cage_enable=1
Why do we need the kernel cage? To address a problem with memory
fragmentation. Immediately after a system boot, a sizeable pool of large pages are
available and the applications can get all of their mmap() memory allocated from
large pages. This can be verified using pmap -xs . If the machine has
been in use for a while, the application may not get the desirable large pages until
the machine is rebooted. This is mainly due to the fragmentation of physical
memory.
We can vastly minimize the fragmentation by enabling the kernel cage. With the
kernel cage enabled, the kernel will be allocated from a small contiguous range of
memory, minimizing the fragmentation of other pages within the system.
2. Find out all possible hardware address translation (HAT) sizes supported by the
system with pagesize -a.
$ pagesize -a
8192
65536
524288
4194304
3. Run trapstat -T. The value shown in the ttl row and %time column is the
percentage of time the processor(s) spent in virtual-to-physical memory address
translations. Depending on %time, make a wise choice of a pagesize that will help
reduce reducing the iTLB/dTLB miss rate.
4. Create a simple config file for MPSS as follows:
oracle*::
Desirable heap and stack size must be one of the supported HAT sizes. By
default, 8Kbytes is the page size for heap and stack on all Solaris releases.
<strong>Performance</strong> <strong>Tuning</strong> <strong>Siebel</strong> <strong>Software</strong> on the Sun Platform Page 45