Steven Rostedt wrote:
On Sun, 31 Aug 2008, Karthik Singaram Lakshmanan wrote:
Hi,
I am a noob to SMP real-time scheduling in linux, I have a question of
sched_setaffinity(). If I restrict an application to a single CPU
using the appropriate cpumask for sched_setaffinity(), Is it
guaranteed that the kernel will never schedule it on any other CPU? I
am asking this because looking at kernel/sched.c seems to use
cpu_clear during load balancing. I am interested in knowing whether the
cache will be invalidated when my task is assigned to a single CPU.
Are there exceptions where the cpu-mask will be overridden?
Thanks for taking the time to answer my query.
A task should never be scheduled on a CPU that is not in its affinity.
(although I hear a rumor that if a task is bound to a single CPU, and that
CPU is taken offline, it will be migrated. But I doubt this is true, since
there are tasks that would crash the system if this were true).
-- Steve
It seems to be true. It's affinity mask gets changed to the CPUs left online.
At least according to sched_getaffinity.
Mark
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