Messages in this thread |  | | Date | Mon, 26 Nov 2001 19:52:20 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: [PATCH] proc-based cpu affinity user interface |
| |
On 26 Nov 2001, Robert Love wrote:
> Attached is my procfs-based implementation of a user interface for > getting and setting a task's CPU affinity. Patch is against 2.4.16. > > The kernel already respects affinity, which is stored in > task_struct->cpus_allowed. > > Reading and writing /proc/<pid>/affinity will get and set the affinity. > > Security is implemented: the writer must possess CAP_SYS_NICE or be the > same uid as the task in question. Anyone can read the data. > > The read mask will be ANDed with cpu_online_map, so that only valid bits > are returned. The written data must have _some_ valid bits in it. > I.e., ffffffff is valid on a 2-way system but 01000000 probably is not. > Note you don't need to pass the full mask, e.g. "64" is legal. When a > new mask is set, a reschedule is forced to put the task on a legal CPU. > > Note I had to implement a proc_write function for the procfs (pid) > code. This is generic and can be used by other, writable, entries. > > This patch comes as an alternative to Ingo Molnar's syscall-implemented > variant. Ingo's code is good; however I and others expressed discontent > at yet another group of syscalls. Other benefits include the ease with > which to set the affinity of tasks that are unaware of the new interface > and that with this approach applications don't need to check for the > existence of a syscall. > > Comments?
As I said in reply to Ingo patch, it'd be better to expose "number" cpu masks not "logical" ( like cpus_allowed ). In this way the users can use 0..N-1 ( N == number of cpus phisically available ) w/out having to know the internal mapping between logical and number ids.
- Davide
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |