job placement on large systems.
Cpusets use the generic cgroup subsystem described in
-Documentation/cgroup.txt.
+Documentation/cgroups/cgroups.txt.
Requests by a task, using the sched_setaffinity(2) system call to
include CPUs in its CPU affinity mask, and using the mbind(2) and
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
The following rules apply to each cpuset:
- Its CPUs and Memory Nodes must be a subset of its parents.
- - It can only be marked exclusive if its parent is.
+ - It can't be marked exclusive unless its parent is.
- If its cpu or memory is exclusive, they may not overlap any sibling.
These rules, and the natural hierarchy of cpusets, enable efficient
flag, and if set, a call to a new routine cpuset_mem_spread_node()
returns the node to prefer for the allocation.
-Similarly, setting 'memory_spread_cache' turns on the flag
+Similarly, setting 'memory_spread_slab' turns on the flag
PF_SPREAD_SLAB, and appropriately marked slab caches will allocate
pages from the node returned by cpuset_mem_spread_node().
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
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.
In this directory you can find several files:
# ls
-cpus cpu_exclusive mems mem_exclusive mem_hardwall tasks
+cpu_exclusive memory_migrate mems tasks
+cpus memory_pressure notify_on_release
+mem_exclusive memory_spread_page sched_load_balance
+mem_hardwall memory_spread_slab sched_relax_domain_level
Reading them will give you information about the state of this cpuset:
the CPUs and Memory Nodes it can use, the processes that are using
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff