On 12/11/2012 07:17 PM, Tejun Heo wrote: > Hello, Srivatsa. > > On Tue, Dec 11, 2012 at 06:43:54PM +0530, Srivatsa S. Bhat wrote: >> This approach (of using synchronize_sched()) also looks good. It is simple, >> yet effective, but unfortunately inefficient at the writer side (because >> he'll have to wait for a full synchronize_sched()). > > While synchornize_sched() is heavier on the writer side than the > originally posted version, it doesn't stall the whole machine and > wouldn't introduce latencies to others. Shouldn't that be enough? >
Short answer: Yes. But we can do better, with almost comparable code complexity. So I'm tempted to try that out. Long answer: Even in the synchronize_sched() approach, we still have to identify the readers who need to be converted to use the new get/put_online_cpus_atomic() APIs and convert them. Then, if we can come up with a scheme such that the writer has to wait only for those readers to complete, then why not? If such a scheme ends up becoming too complicated, then I agree, we can use synchronize_sched() itself. (That's what I meant by saying that we'll use this as a fallback). But even in this scheme which uses synchronize_sched(), we are already half-way through (we already use 2 types of sync schemes - counters and rwlocks). Just a little more logic can get rid of the unnecessary full-wait too.. So why not give it a shot? Regards, Srivatsa S. Bhat -- 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/