On 03/22/2013 01:14 PM, Preeti U Murthy wrote: >> > >> > the value get from decay_load(): >> > sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum, >> > in decay_load it is possible to be set zero. > Yes you are right, it is possible to be set to 0, but after a very long > time, to be more precise, nearly 2 seconds. If you look at decay_load(), > if the period between last update and now has crossed (32*63),only then > will the runnable_avg_sum become 0, else it will simply decay. > > This means that for nearly 2seconds,consolidation of loads may not be > possible even after the runqueues have finished executing tasks running > on them.
Look into the decay_load(), since the LOAD_AVG_MAX is about 47742, so after 16 * 32ms, the maximum avg sum will be decay to zero. 2^16 = 65536 Yes, compare to accumulate time 345ms, the decay is not symmetry, and not precise, seems it has space to tune well. But it is acceptable now. > > The exact experiment that I performed was running ebizzy, with just two > threads. My setup was 2 socket,2 cores each,4 threads each core. So a 16 > logical cpu machine.When I begin running ebizzy with balance policy, the > 2 threads of ebizzy are found one on each socket, while I would expect > them to be on the same socket. All other cpus, except the ones running > ebizzy threads are idle and not running anything on either socket. > I am not running any other processes. did you try the simplest benchmark: while true; do :; done I am writing the v6 version which include rt_util etc. you may test on it after I send out. :) > > You could run a similar experiment and let me know if you see otherwise. > I am at a loss to understand why else would such a spreading of load > occur, if not for the rq->util not becoming 0 quickly,when it is not > running anything. I have used trace_printks to keep track of runqueue > util of those runqueues not running anything after maybe some initial > load and it does not become 0 till the end of the run. -- Thanks Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
