On Thu, Apr 09, 2015 at 08:02:28AM -0400, Chris Metcalf wrote: > On 4/9/2015 4:29 AM, Peter Zijlstra wrote: > >On Wed, Apr 08, 2015 at 02:12:34PM -0400, Chris Metcalf wrote: > > > >>>But you're doing the reverse! You're setting nohz_full for isolcpus, not > >>>limiting the nohz_full mask to isolcpus. > >>Ah, I see. Yes, that's right. > >No its not, you should correct me when I'm wrong ;-) > > Oh, I have no problem with that :-) But, now that I know what was confusing > you about the patch I see what it was you were saying with your English > above too. I thought you were saying something like "making nohz_full > imply isolcpus" again, but you weren't. Phew, OK, I think we're done > talking at cross-purposes. > > >So the problem is that: > > > >+ tick_nohz_full_set_cpus(cpu_isolated_map); > > > >reads like you're doing: > > > > nohz_full_map |= isolcpus_map > > > >But in actual fact you're doing: > > > > isolcpus_map |= nohz_full_map > > > >So that function is retarded, but the logic is fine. > > > >So NAK on both patches for the reason that they're utterly confusing as > >to wtf they actually do. > > What about tick_nohz_full_cpumask_or(cpu_isolated_map) ? > At that point maybe the similarity to the existing cpumask API will make > it more clear that we are modifying the argument? > > If not, do you have any suggestions what might do better? Obviously > the goal is to make it something that macroizes away, otherwise I'd > suggest just explicitly using an #ifdef and cpumask_or().
Possible alternative: do it the other way around. cpu_isolated_map is allocated and filled early (__setup or sched_init()) before tick_init() and tick_init() is before sched_init_smp() which first uses cpu_isolated_map(). So we can call some sched_isolated_map_add(struct cpumask *cpumask) from tick_nohz_init(). -- 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/
