On Thu, Jan 5, 2017 at 1:01 PM, Andres Freund <and...@anarazel.de> wrote:
> Hi, > > On 2017-01-05 12:55:44 -0600, Jonathon Nelson wrote: > > Attached please find a patch for PostgreSQL 9.4 which changes the maximum > > amount of data that the wal sender will send at any point in time from > the > > hard-coded value of 128KiB to a user-controllable value up to 16MiB. It > has > > been primarily tested under 9.4 but there has been some testing with 9.5. > > > > In our lab environment and with a 16MiB setting, we saw substantially > > better network utilization (almost 2x!), primarily over high bandwidth > > delay product links. > > That's a bit odd - shouldn't the OS network stack take care of this in > both cases? I mean either is too big for TCP packets (including jumbo > frames). What type of OS and network is involved here? > In our test lab, we make use of multiple flavors of Linux. No jumbo frames. We simulated anything from 0 to 160ms RTT (with varying degrees of jitter, packet loss, etc.) using tc. Even with everything fairly clean, at 80ms RTT there was a 2x improvement in performance. -- Jon Nelson Dyn / Principal Software Engineer
