Red Hat ENTERPRISE LINUX 4 - INTRODUCTION TO SYSTEM ADMINISTRATION Administration Manual page 67

Chapter 4. Physical and Virtual Memory
The and
kbmemfree
percentage of memory used displayed in the
show how many kilobytes of memory are allocated to buffers and the system-wide data cache.
The field is always zero for systems (such as Red Hat Enterprise Linux) using the 2.4
kbmemshrd
Linux kernel.
The lines for this report have been truncated to fit on the page. Here is the remainder of each line, with
the timestamp added to the left to make reading easier:
12:00:01 AM kbswpfree kbswpused
12:10:00 AM
12:20:00 AM
...
08:40:00 PM
Average:
For swap utilization, the
space, in kilobytes, with the
To learn more about the swapping activity taking place, use the
Linux 2.4.20-1.1931.2.231.2.10.entsmp (raptor.example.com)
12:00:01 AM pswpin/s pswpout/s
12:10:01 AM
12:20:00 AM
...
03:30:01 PM
Average:
Here we notice that, on average, there were three times fewer pages being brought in from swap
( ) as there were going out to swap (
pswpin/s
To better understand how pages are being used, refer to the
Linux 2.4.20-1.1931.2.231.2.10.entsmp (raptor.example.com)
12:00:01 AM pgpgin/s pgpgout/s
12:10:00 AM
12:20:00 AM
...
08:40:00 PM
Average: 201.54
Here we can determine how many blocks per second are paged in from disk (
out to disk (
pgpgout/s
However, more knowledge can be gained by examining the other fields in this report. The Red Hat
Enterprise Linux kernel marks all pages as either active or inactive. As the names imply, active pages
are currently in use in some manner (as process or buffer pages, for example), while inactive pages
are not. This example report shows that the list of active pages (the
3
imately 660MB .
The remainder of the fields in this report concentrate on the inactive list — pages that, for one reason
or another, have not recently been used. The
3. The page size under Red Hat Enterprise Linux on the x86 system used in this example is 4096 bytes. Systems
based on other architectures may have different page sizes.
fields show the typical free and used memory statistics, with the
kbmemused
522104 0
522104 0
522104 0
522104 0
and
kbswpfree
field showing the swap space used as a percentage.
%swpused
0.15 2.56
0.00 0.00
0.42 2.56
0.11 0.37
activepg
0.03 8.61
0.01 7.51
0.00 7.79
201.54
). These statistics serve as a barometer of overall virtual memory activity.
field. The
%memused
%swpused
0.00
0.00
0.00
0.00
fields show the amount of free and used swap
kbswpused
).
pswpout/s
sar -B
inadtypg
195393 20654
195385 20655
71236 1371
169367 18999
field shows how many inactive pages are dirty
inadtypg
and
kbbuffers kbcached
report. Here is an example:
sar -W
07/22/2003
report:
07/22/2003
inaclnpg inatarpg
30352 49279
30336 49275
6760 15873
35146 44702
pgpgin/s
field) averages approx-
activepg
55
fields
) and paged