On 2015-07-09 04:45:38 +0200, Mike Galbraith wrote: > On Wed, 2015-07-08 at 17:45 +0200, Andres Freund wrote: > > Workload: > > > > postgresql (multi-process via shared memory SQL server) and benchmark > > client (pgbench, multi threaded) running on the same server. Connected > > using unix sockets. The statements are relatively simple (~1.5ms on > > average), forcing frequent back/forth between server processes and > > pgbench threads. > > > > I found that disabling sched_autogroup *significantly* reduces > > throughput. Even when both server and client are started from the same > > terminal and thus should be in the same group! > > > > There's a significant difference in how %sys with autogroups > > enabled/disabled. ~8% v ~27%. That sounds too much. > > Seems reasonable to me. 1(tg)/2(tgs) > 1(task)/N(tasks), throughput is > what the server can sustain on its given budget, larger budget means > less client blockage, thus less %sys.
That'd make some sense if there were other stuff going on - but here the same total budget in both cases leads to a 40% difference in throughput: autogroup on: tps = 21329.219141; autogroup off: tps = 15006.317841 there's really nothing to do for the kernel or other tasks in the background. It's a readonly workload, not requiring lots of memory, ... -- 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/
