IBM REDP-4285-00 User Manual
4285ch02.fm
Draft Document for Review May 4, 2007 11:35 am
48
Linux Performance and Tuning Guidelines
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You can also determine much chunks of memory are available in each zone using
/proc/buddyinfo
/proc/buddyinfo
file. Each column of numbers means the number of pages of that order
which are available. In Example 2-10, there are 5 chunks of 2^2*PAGE_SIZE available in
ZONE_DMA, and 16 chunks of 2^4*PAGE_SIZE available in ZONE_DMA32. Remember how
the buddy system allocate pages (refer to “Buddy system” on page 14). This information show
you how fragmented memory is and give you a clue as to how much pages you can safely
allocate.
ZONE_DMA, and 16 chunks of 2^4*PAGE_SIZE available in ZONE_DMA32. Remember how
the buddy system allocate pages (refer to “Buddy system” on page 14). This information show
you how fragmented memory is and give you a clue as to how much pages you can safely
allocate.
Example 2-10 Buddy system information for 64 bit system
[root@lnxsu5 ~]# cat /proc/buddyinfo
Node 0, zone DMA 1 3 5 4 6 1 1 0 2 0 2
Node 0, zone DMA32 56 14 2 16 7 3 1 7 41 42 670
Node 0, zone Normal 0 6 3 2 1 0 1 0 0 1 0
Node 0, zone DMA 1 3 5 4 6 1 1 0 2 0 2
Node 0, zone DMA32 56 14 2 16 7 3 1 7 41 42 670
Node 0, zone Normal 0 6 3 2 1 0 1 0 0 1 0
2.3.6 iostat
The iostat command shows average CPU times since the system was started (similar to
uptime
uptime
). It also creates a report of the activities of the disk subsystem of the server in two
parts: CPU utilization and device (disk) utilization. To use iostat to perform detailed I/O
bottleneck and performance tuning, see 3.4.1, “Finding disk bottlenecks” on page 84. The
iostat utility is part of the sysstat package.
bottleneck and performance tuning, see 3.4.1, “Finding disk bottlenecks” on page 84. The
iostat utility is part of the sysstat package.
Example 2-11 Sample output of iostat
Linux 2.4.21-9.0.3.EL (x232) 05/11/2004
avg-cpu: %user %nice %sys %idle
0.03 0.00 0.02 99.95
0.03 0.00 0.02 99.95
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
dev2-0 0.00 0.00 0.04 203 2880
dev8-0 0.45 2.18 2.21 166464 168268
dev8-1 0.00 0.00 0.00 16 0
dev8-2 0.00 0.00 0.00 8 0
dev8-3 0.00 0.00 0.00 344 0
dev2-0 0.00 0.00 0.04 203 2880
dev8-0 0.45 2.18 2.21 166464 168268
dev8-1 0.00 0.00 0.00 16 0
dev8-2 0.00 0.00 0.00 8 0
dev8-3 0.00 0.00 0.00 344 0
The CPU utilization report has four sections:
%user
Shows the percentage of CPU utilization that was taken up while executing at
the user level (applications).
the user level (applications).
%nice
Shows the percentage of CPU utilization that was taken up while executing at
the user level with a nice priority. (Priority and nice levels are described in
2.3.7, “nice, renice” on page 67.)
the user level with a nice priority. (Priority and nice levels are described in
2.3.7, “nice, renice” on page 67.)
%sys
Shows the percentage of CPU utilization that was taken up while executing at
the system level (kernel).
the system level (kernel).
%idle
Shows the percentage of time the CPU was idle.
The device utilization report has these sections:
Device
The name of the block device.