On Sun, May 3, 2015 at 10:30 AM, Rik van Riel <r...@redhat.com> wrote: > On 05/03/2015 09:23 AM, Mike Galbraith wrote: > >> Below are v4.1-rc1-172-g6c3c1eb3c35e + patches measurements. >> >> 100M * stat() on isolated cpu >> >> NO_HZ_FULL off inactive housekeeper nohz_full >> real 0m14.266s 0m14.367s 0m20.427s 0m27.921s >> user 0m1.756s 0m1.553s 0m1.976s 0m10.447s >> sys 0m12.508s 0m12.769s 0m18.400s 0m17.464s >> (real) 1.000 1.007 1.431 1.957 >> 1.000 1.000 >> >> real 0m20.423s 0m27.930s +rik 1,2 >> user 0m2.072s 0m10.450s >> sys 0m18.304s 0m17.471s >> vs off 1.431 1.957 >> vs prev 1.000 1.000 >> >> real 0m20.256s 0m27.803s +paolo 1,2 (2 >> missing prototypes) >> user 0m1.884s 0m10.551s >> sys 0m18.353s 0m17.242s >> vs off 1.419 1.948 >> vs prev .991 .995 >> >> real 0m19.122s 0m26.946s +rik 3 >> user 0m1.896s 0m10.292s >> sys 0m17.198s 0m16.644s >> vs off 1.340 1.888 >> vs prev .944 .969 > > I'm convinced. > > Time to try the remote sampling of CPU use statistics, and > lighten up the RCU overhead of context tracking. >
I don't understand the remote sampling proposal. Isn't the whole point of full nohz to avoid periodically interrupting a busy CPU? If what you have in mind is sending IPIs, then that's just as bad, right? If, on the other hand, you're just going to remotely sample the in-memory context, that sounds good. --Andy -- 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/
