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| -rw-r--r-- | Documentation/cpusets.txt | 23 |
1 files changed, 8 insertions, 15 deletions
diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt index 141bef1c859..43db6fe1281 100644 --- a/Documentation/cpusets.txt +++ b/Documentation/cpusets.txt @@ -523,21 +523,14 @@ from one cpuset to another, then the kernel will adjust the tasks 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, |