All these are best guesses. On Mon, Apr 19, 2010 at 3:15 PM, Primiano Tucci <p.tucci@xxxxxxxxx> wrote: > Hi all, > I am an Italian researcher and I am working on a Real Time scheduling > infrastructure. I am currently using Linux Kernel 2.6.29.6-rt24-smp > (PREEMPT-RT Patch) running on a Intel Q9550 CPU. > I am experiencing strange behaviors with the pthread_setaffinity_np API. > > This is my scenario, I have 4 Real Time Threads (SCHED_FIFO) > distributed as follows: > > T0 : CPU 0, Priority 2 (HIGH) > T1 : CPU 1, Priority 2 (HIGH) > T3 : CPU 0, Priority 1 (LOW) > T4 : CPU 1, Priority 1 (LOW) Could you check with the manual whether the following documentation specifies your Processor. http://www.intel.com/design/core2quad/documentation.htm The reason I am asking is that what ever you are stating above in terms of thread affinity would not even qualify as an Core2duo. > > So T0 and T1 are actually the "big bosses" on CPUs #0 and #1, T3 and > T4, instead, never execute (let's assume that each thread is a simple > busy wait that never sleeps/yields) > Now, at a certain point, from T0 code, I want to migrate T4 from CPU > #1 to #0, keeping its low priority. > Therefore I perform a pthread_setaffinity_np from T0 changing T4 mask > from CPU #1 to #0. This approach is not at all correct as the thread affinity should be closer to the core than the processor. If this is supported. > > In this scenario it happens that T3 (that should never execute since > there is T0 with higher priority currently running on the same CPU #0) > "emerge" and executes for a bit. > It seems that the pthread_setaffinity_np syscall is somehow > "suspensive" for the time needed to migrate T4 and let the scheduler > to execute T3 for that bunch of time. I think what is happening is that Once you have scheduled the code on processor basis, It tends to ignore core logic, but depends more on the processor logic. > > Is this behavior expected (I did not find any documentation about > this)? How can avoid it? I think you will have to set the affinity to core level than at processor level. > > Thanks in advance, > Primiano > > -- > Primiano Tucci > http://www.primianotucci.com > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- -- Sujit K M blog(http://kmsujit.blogspot.com/) -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
