2007-Dec-6 - Linux Performance Monitoring - study notes
1. Start with the output of vmstat or mpstat for a dashboard of system performance.
# vmstat 1 10
1 second interval for 10 seconds
Field Description
--- CPU performance ---
R The amount of threads in the run queue. These are threads that are runnable, but the CPU is not available to execute them.
B This is the number of processes blocked and waiting on IO requests to finish.
In This is the number of interrupts being processed.
Cs This is the number of context switches currently happening on the system.
Us This is the percentage of user CPU utilization.
Sys This is the percentage of kernel and interrupts utilization.
Wa This is the percentage of idle processor time due to the fact that ALL runnable threads are blocked waiting on IO.
Id This is the percentage of time that the CPU is completely idle.
--- virtual memory ---
Swapd The amount of virtual memory in KB currently in use. As free memory reaches low thresholds, more data is paged to the swap device.
Free The amount of physical RAM in kilobytes currently available to running applications.
Buff The amount of physical memory in kilobytes in the buffer cache as a result of read() and write() operations.
Cache The amount of physical memory in kilobytes mapped into process address space.
so The amount of data in kilobytes written to the swap disk.
si The amount of data in kilobytes written from the swap disk back into RAM.
Bo The amount of disk blocks paged out from the RAM to the filesystem or swap device.
Bi The amount of disk blocks paged into RAM from the filesystem or swap device.
also
# mpstat -P ALL 1 10
breaks the statistics out on a per processor basis.
2. Use iostat to determine from where the read requests are being generated.
# iostat -x 1
3. Using top, determine what application is most active on the system
# top -d 1
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