Chapter 24. 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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2. Alternatively, view a specific thread corresponding to a PID or matching a command name:

   # 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.

3. Depending on the 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.

4. 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 currently running processes:

   # 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. Depending on your scenario, use this command to manage CPU affinity of processes with one of the following actions:

   # 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:

   1. To isolate a CPU, enter:

      # tuna isolate --cpus cpu_list

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   2. 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*

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   # 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.

Verification

1. Compare the state of the selected IRQs before and after moving any interrupt to a specified CPU:

   # tuna show_irqs --irqs 128
        users            affinity
    128 iwlwifi                 3

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   For more information, see the /proc/interrupts file and the tuna(8) man page on your system.