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.
-Mike
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