diff options
Diffstat (limited to 'Documentation/cpusets.txt')
| -rw-r--r-- | Documentation/cpusets.txt | 29 |
1 files changed, 18 insertions, 11 deletions
diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt index d803c5c68ab..47e568a9370 100644 --- a/Documentation/cpusets.txt +++ b/Documentation/cpusets.txt @@ -154,13 +154,15 @@ browsing and modifying the cpusets presently known to the kernel. No new system calls are added for cpusets - all support for querying and modifying cpusets is via this cpuset file system. -The /proc/<pid>/status file for each task has two added lines, +The /proc/<pid>/status file for each task has four added lines, displaying the tasks cpus_allowed (on which CPUs it may be scheduled) and mems_allowed (on which Memory Nodes it may obtain memory), -in the format seen in the following example: +in the two formats seen in the following example: Cpus_allowed: ffffffff,ffffffff,ffffffff,ffffffff + Cpus_allowed_list: 0-127 Mems_allowed: ffffffff,ffffffff + Mems_allowed_list: 0-63 Each cpuset is represented by a directory in the cgroup file system containing (on top of the standard cgroup files) the following @@ -542,7 +544,10 @@ otherwise initial value -1 that indicates the cpuset has no request. 2 : search cores in a package. 3 : search cpus in a node [= system wide on non-NUMA system] ( 4 : search nodes in a chunk of node [on NUMA system] ) - ( 5~ : search system wide [on NUMA system]) + ( 5 : search system wide [on NUMA system] ) + +The system default is architecture dependent. The system default +can be changed using the relax_domain_level= boot parameter. This file is per-cpuset and affect the sched domain where the cpuset belongs to. Therefore if the flag 'sched_load_balance' of a cpuset @@ -630,14 +635,16 @@ prior 'mems' setting, will not be moved. There is an exception to the above. If hotplug functionality is used to remove all the CPUs that are currently assigned to a cpuset, -then the kernel will automatically update the cpus_allowed of all -tasks attached to CPUs in that cpuset to allow all CPUs. When memory -hotplug functionality for removing Memory Nodes is available, a -similar exception is expected to apply there as well. In general, -the kernel prefers to violate cpuset placement, over starving a task -that has had all its allowed CPUs or Memory Nodes taken offline. User -code should reconfigure cpusets to only refer to online CPUs and Memory -Nodes when using hotplug to add or remove such resources. +then all the tasks in that cpuset will be moved to the nearest ancestor +with non-empty cpus. But the moving of some (or all) tasks might fail if +cpuset is bound with another cgroup subsystem which has some restrictions +on task attaching. In this failing case, those tasks will stay +in the original cpuset, and the kernel will automatically update +their cpus_allowed to allow all online CPUs. When memory hotplug +functionality for removing Memory Nodes is available, a similar exception +is expected to apply there as well. In general, the kernel prefers to +violate cpuset placement, over starving a task that has had all +its allowed CPUs or Memory Nodes taken offline. There is a second exception to the above. GFP_ATOMIC requests are kernel internal allocations that must be satisfied, immediately. |