At Thu, 30 Apr 2009 11:46:05 -0700, Jonathan Petersson <jpeters...@garnser.se> wrote:
> I've been running some dnsperf tests on a couple of servers I have > resulting in some interesting behaviors. [...] > Any input would be valuable, thanks! Roughly summarizing (ignoring many details), what you showed is: 2 threads on 2 core: 45kqps 4 threads on 4 core: 108kkqps 8 threads on 4 core + HT: 75kqps 16 threads on 8 core + HT: 35kqps correct? There are several possible explanations. First, you may be using too many threads when you see lower performance. Even though recent versions of BIND9 tries very hard eliminating inter-thread contention, it cannot completely be free from some inherent overhead with the use of multiple threads, which could be revealed as you increase the number of threads. From my past experiences threaded BIND9 scales pretty well with at least up to 4 threads (on 4 cores), and I believe it also works well with additional 1-2 threads. I'm not sure about 8 threads, and I've heard a report of performance degradation at around this number. Second, again, from my past personal experiences, HT never helped BIND9; rather, it often worsened the performance. I've not figured out why; if it really works as the manufacturer claims (e.g., using a single core efficiently with multiple threads when one thread stalls due to memory access), it could actually improve overall performance. But empirical experiments have always denied the theoretical positive effect. Note: I've not tried Intel's latest "hyper threading" (Now called SMT), so my experience was limited to older versions of HT. --- JINMEI, Tatuya Internet Systems Consortium, Inc. _______________________________________________ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
