On 02/20/2015 03:57 PM, Paolo Bonzini wrote: > > > On 20/02/2015 15:54, Sebastian Andrzej Siewior wrote: >> Usually you see "scheduling while atomic" on -RT and convert them to >> raw locks if it is appropriate. >> >> Bogdan wrote in 2/2 that he needs to limit the number of CPUs in oder >> not cause a DoS and large latencies in the host. I haven't seen an >> answer to my why question. Because if the conversation leads to >> large latencies in the host then it does not look right. >> >> Each host PIC has a rawlock and does mostly just mask/unmask and the >> raw lock makes sure the value written is not mixed up due to >> preemption. >> This hardly increase latencies because the "locked" path is very short. >> If this conversation leads to higher latencies then the locked path is >> too long and hardly suitable to become a rawlock. > > Yes, but large latencies just mean the code has to be rewritten (x86 > doesn't anymore do event injection in an atomic regions for example). > Until it is, using raw_spin_lock is correct. It does not sound like it. It sounds more like disabling interrupts to get things run faster and then limit it on a different corner to not blow up everything. Max latencies was decreased "Max latency (us) 70 62" and that is why this is done? For 8 us and possible DoS in case there are too many cpus? > Paolo > Sebastian -- 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
