memory placement, as above, the next time that the kernel attempts
to allocate a page of memory for that task.
-If a cpuset has its CPUs modified, then each task using that
-cpuset does _not_ change its behavior automatically. In order to
-minimize the impact on the critical scheduling code in the kernel,
-tasks will continue to use their prior CPU placement until they
-are rebound to their cpuset, by rewriting their pid to the 'tasks'
-file of their cpuset. If a task had been bound to some subset of its
-cpuset using the sched_setaffinity() call, and if any of that subset
-is still allowed in its new cpuset settings, then the task will be
-restricted to the intersection of the CPUs it was allowed on before,
-and its new cpuset CPU placement. If, on the other hand, there is
-no overlap between a tasks prior placement and its new cpuset CPU
-placement, then the task will be allowed to run on any CPU allowed
-in its new cpuset. If a task is moved from one cpuset to another,
-its CPU placement is updated in the same way as if the tasks pid is
-rewritten to the 'tasks' file of its current cpuset.
+If a cpuset has its 'cpus' modified, then each task in that cpuset
+will have its allowed CPU placement changed immediately. Similarly,
+if a tasks pid is written to a cpusets 'tasks' file, in either its
+current cpuset or another cpuset, then its allowed CPU placement is
+changed immediately. If such a task had been bound to some subset
+of its cpuset using the sched_setaffinity() call, the task will be
+allowed to run on any CPU allowed in its new cpuset, negating the
+affect of the prior sched_setaffinity() call.
In summary, the memory placement of a task whose cpuset is changed is
updated by the kernel, on the next allocation of a page for that task,
git.samba.org / sfrench / cifs-2.6.git / blobdiff