IBM REDP-4285-00 User Manual
Chapter 3. Analyzing performance bottlenecks
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Draft Document for Review May 4, 2007 11:35 am
4285ch03.fm
Figure 3-1 KDE System Guard memory monitoring
The indicators in Table 3-1 can also help you define a problem with memory.
Table 3-1 Indicator for memory analysis
Paging and swapping indicators
In Linux, as with all UNIX-based operating systems, there are differences between paging
and swapping. Paging moves individual pages to swap space on the disk; swapping is a
bigger operation that moves the entire address space of a process to swap space in one
operation.
and swapping. Paging moves individual pages to swap space on the disk; swapping is a
bigger operation that moves the entire address space of a process to swap space in one
operation.
Swapping can have one of two causes:
A process enters sleep mode. This usually happens because the process depends on
interactive action, as editors, shells, and data entry applications spend most of their time
waiting for user input. During this time, they are inactive.
interactive action, as editors, shells, and data entry applications spend most of their time
waiting for user input. During this time, they are inactive.
Memory indicator
Analysis
Memory available
This indicates how much physical memory is available for use. If, after you start your application,
this value has decreased significantly, you may have a memory leak. Check the application that
is causing it and make the necessary adjustments. Use free -l -t -o for additional information.
this value has decreased significantly, you may have a memory leak. Check the application that
is causing it and make the necessary adjustments. Use free -l -t -o for additional information.
Page faults
There are two types of page faults: soft page faults, when the page is found in memory, and hard
page faults, when the page is not found in memory and must be fetched from disk. Accessing
the disk will slow your application considerably. The sar -B command can provide useful
information for analyzing page faults, specifically columns pgpgin/s and pgpgout/s.
page faults, when the page is not found in memory and must be fetched from disk. Accessing
the disk will slow your application considerably. The sar -B command can provide useful
information for analyzing page faults, specifically columns pgpgin/s and pgpgout/s.
File system cache
This is the common memory space used by the file system cache. Use the free -l -t -o
command for additional information.
command for additional information.
Private memory for
process
process
This represents the memory used by each process running on the server. You can use the pmap
c
c
ommand to see how much memory is allocated to a specific process.