Chapter 4. Reviewing a system by using the tuna interface

Procedure

1. View the current policies and priorities:

   # tuna show_threads
   pid   SCHED_ rtpri affinity             cmd
   1      OTHER     0      0,1            init
   2       FIFO    99        0     migration/0
   3      OTHER     0        0     ksoftirqd/0
   4       FIFO    99        0      watchdog/0

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   Alternatively, to view a specific thread corresponding to a PID or matching a command name, enter:

   # tuna show_threads -t pid_or_cmd_list

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   The pid_or_cmd_list argument is a list of comma-separated PIDs or command-name patterns.

2. Depending on you scenario, perform one of the following actions:

   • To tune CPUs by using the tuna CLI, complete the steps in Tuning CPUs by using the tuna tool.
   • To tune the IRQs by using the tuna tool, complete the steps in Tuning IRQs by using the tuna tool.

3. Save the changed configuration:

   # tuna save filename

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   This command saves only currently running kernel threads. Processes that are not running are not saved.

Procedure

1. List all CPUs and specify the list of CPUs to be affected by the command:

   # ps ax | awk 'BEGIN { ORS="," }{ print $1 }'
   PID,1,2,3,4,5,6,8,10,11,12,13,14,15,16,17,19

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2. Display the thread list in the tuna interface:

   # tuna show_threads -t 'thread_list from above cmd'

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3. Specify the list of CPUs to be affected by a command:

   # *tuna [command] --cpus cpu_list *

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   The cpu_list argument is a list of comma-separated CPU numbers, for example, --cpus 0,2.

   To add a specific CPU to the current cpu_list, use, for example, --cpus +0.

4. Depending on your scenario, perform one of the following actions:

   • To isolate a CPU, enter:

     # tuna isolate --cpus cpu_list

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   • To include a CPU, enter:

     # tuna include --cpus cpu_list

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5. To use a system with four or more processors, make all ssh threads run on CPU 0 and 1 and all http threads on CPU 2 and 3:

   # tuna move --cpus 0,1 -t ssh*
   # tuna move --cpus 2,3 -t http\*

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Procedure

1. View the current IRQs and their affinity:

   # tuna show_irqs
   # users            affinity
   0 timer                   0
   1 i8042                   0
   7 parport0                0

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2. Specify the list of IRQs to be affected by a command:

   # tuna [command] --irqs irq_list --cpus cpu_list

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   The irq_list argument is a list of comma-separated IRQ numbers or user-name patterns.

   Replace [command] with, for example, --spread.

3. Move an interrupt to a specified CPU:

   # tuna show_irqs --irqs 128
   users            affinity
   128 iwlwifi           0,1,2,3
   
   # tuna move --irqs 128 --cpus 3

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   Replace 128 with the irq_list argument and 3 with the cpu_list argument.

   The cpu_list argument is a list of comma-separated CPU numbers, for example, --cpus 0,2. For more information, see Tuning CPUs by using the tuna tool.