Installation guide

the noop scheduler for device /dev/sdd and verify the result:

# echo noop > /sys/block/sdd/queue/scheduler

# cat /sys/block/sdd/queue/scheduler

[noop] anticipatory deadline cfq

RHEL5 Running as a VMware Guest

By default, the timer interrupt (tick) rate in Red Hat Enterprise Linux 4 and 5 is 1000 Hz. In some situations,

this rate is too high, with frequent interrupts potentially causing a performance impact or unexpected behavior.

This impact would be most notable when running Red Hat Enterprise Linux as a virtual guest. For example,

with the 1000 Hz tick rate, time drift might be observed in a virtual environment.

To compensate for the fact that different workloads and different environments work better with different tick

rates, a new kernel parameter was added to Red Hat Enterprise Linux 5.1 and 4.7. This kernel parameter, "di-

vider", is a boot-time setting that allows the user to divide the tick rate by the desired amount. For example, set-

ting the divider to 10 would cause the default tick rate to be 1000/10, or 100 Hz.

The divider parameter can be set by appending "divider=N" to the kernel boot line in /boot/grub/grub.-

conf.

The recommended kernel line settings for 64-bit Red Hat Enterprise Linux 5 running as a VMware guest are:

divider=10 notsc iommu=soft elevator=noop

and for a 32-bit Red Hat Enterprise Linux 5 Vmware guest:

divider=10 clocksource=acpi_pm iommu=soft elevator=noop

Memory Usage and Page Cache

Checking Memory Usage

To determine the size and usage of memory, you can enter the following command:

$ grep MemTotal /proc/meminfo

Alternatively, you can use the free(1) command to check the memory:

$ free

total used free shared buffers cached

Mem: 4040360 4012200 28160 0 176628 3571348

-/+ buffers/cache: 264224 3776136

Swap: 4200956 12184 4188772

In this example the total amount of available memory is 4040360 KB. 264224 KB are used by processes and