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-rw-r--r--bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.xml50
1 files changed, 50 insertions, 0 deletions
diff --git a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.xml b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.xml
index 9e4551be1c..e5aeffcffb 100644
--- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.xml
+++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.xml
@@ -856,6 +856,56 @@
856 </glossdef> 856 </glossdef>
857 </glossentry> 857 </glossentry>
858 858
859 <glossentry id='var-BB_TASK_IONICE_LEVEL'><glossterm>BB_TASK_IONICE_LEVEL</glossterm>
860 <glossdef>
861 <para>
862 Allows adjustment of a task's Input/Output priority.
863 During Autobuilder testing, random failures can occur
864 for tasks due to I/O starvation.
865 These failures occur during various QEMU runtime timeouts.
866 You can use the <filename>BB_TASK_IONICE_LEVEL</filename>
867 variable to adjust the I/O priority of these tasks.
868 <note>
869 This variable works similarly to the
870 <link linkend='var-BB_TASK_NICE_LEVEL'><filename>BB_TASK_NICE_LEVEL</filename></link>
871 variable except with a task's I/O priorities.
872 </note>
873 </para>
874
875 <para>
876 Set the variable as follows:
877 <literallayout class='monospaced'>
878 BB_TASK_IONICE_LEVEL = "<replaceable>class</replaceable>.<replaceable>prio</replaceable>"
879 </literallayout>
880 For <replaceable>class</replaceable>, the default value is
881 "2", which is a best effort.
882 You can use "1" for realtime and "3" for idle.
883 If you want to use realtime, you must have superuser
884 privileges.
885 </para>
886
887 <para>
888 For <replaceable>prio</replaceable>, you can use any
889 value from "0", which is the highest priority, to "7",
890 which is the lowest.
891 The default value is "4".
892 You do not need any special privileges to use this range
893 of priority values.
894 <note>
895 In order for your I/O priority settings to take effect,
896 you need the Completely Fair Queuing (CFQ) Scheduler
897 selected for the backing block device.
898 To select the scheduler, use the following command form
899 where <replaceable>device</replaceable> is the device
900 (e.g. sda, sdb, and so forth):
901 <literallayout class='monospaced'>
902 $ sudo sh -c “echo cfq > /sys/block/<replaceable>device</replaceable>/queu/scheduler
903 </literallayout>
904 </note>
905 </para>
906 </glossdef>
907 </glossentry>
908
859 <glossentry id='var-BB_TASK_NICE_LEVEL'><glossterm>BB_TASK_NICE_LEVEL</glossterm> 909 <glossentry id='var-BB_TASK_NICE_LEVEL'><glossterm>BB_TASK_NICE_LEVEL</glossterm>
860 <glossdef> 910 <glossdef>
861 <para> 911 <para>