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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 141bef1c8599..43db6fe12814 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 | |||
| 523 | memory placement, as above, the next time that the kernel attempts | 523 | memory placement, as above, the next time that the kernel attempts |
| 524 | to allocate a page of memory for that task. | 524 | to allocate a page of memory for that task. |
| 525 | 525 | ||
| 526 | If a cpuset has its CPUs modified, then each task using that | 526 | If a cpuset has its 'cpus' modified, then each task in that cpuset |
| 527 | cpuset does _not_ change its behavior automatically. In order to | 527 | will have its allowed CPU placement changed immediately. Similarly, |
| 528 | minimize the impact on the critical scheduling code in the kernel, | 528 | if a tasks pid is written to a cpusets 'tasks' file, in either its |
| 529 | tasks will continue to use their prior CPU placement until they | 529 | current cpuset or another cpuset, then its allowed CPU placement is |
| 530 | are rebound to their cpuset, by rewriting their pid to the 'tasks' | 530 | changed immediately. If such a task had been bound to some subset |
| 531 | file of their cpuset. If a task had been bound to some subset of its | 531 | of its cpuset using the sched_setaffinity() call, the task will be |
| 532 | cpuset using the sched_setaffinity() call, and if any of that subset | 532 | allowed to run on any CPU allowed in its new cpuset, negating the |
| 533 | is still allowed in its new cpuset settings, then the task will be | 533 | affect of the prior sched_setaffinity() call. |
| 534 | restricted to the intersection of the CPUs it was allowed on before, | ||
| 535 | and its new cpuset CPU placement. If, on the other hand, there is | ||
| 536 | no overlap between a tasks prior placement and its new cpuset CPU | ||
| 537 | placement, then the task will be allowed to run on any CPU allowed | ||
| 538 | in its new cpuset. If a task is moved from one cpuset to another, | ||
| 539 | its CPU placement is updated in the same way as if the tasks pid is | ||
| 540 | rewritten to the 'tasks' file of its current cpuset. | ||
| 541 | 534 | ||
| 542 | In summary, the memory placement of a task whose cpuset is changed is | 535 | In summary, the memory placement of a task whose cpuset is changed is |
| 543 | updated by the kernel, on the next allocation of a page for that task, | 536 | updated by the kernel, on the next allocation of a page for that task, |