Re: something is wonky with pgbench pipelining

Hi,

Adding RMT.

On 2021-07-21 16:55:08 -0700, Andres Freund wrote:
> On 2021-07-20 14:57:15 -0400, Alvaro Herrera wrote:
> > On 2021-Jul-20, Andres Freund wrote:
> > 
> > > I think what's happening is that the first recvfrom() actually gets all 7
> > > connection results. The server doesn't have any queries to process at that
> > > point. But we ask the kernel whether there is new network input over and over
> > > again, despite having results to process!
> > 
> > Hmm, yeah, that seems a missed opportunity.
> 
> > > with-isbusy:
> > > ...
> > > tps = 3990.424742 (without initial connection time)
> > > ...
> > >           1,013.71 msec task-clock                #    0.202 CPUs utilized
> > >             80,203      raw_syscalls:sys_enter    #   79.119 K/sec
> > >             19,947      context-switches          #   19.677 K/sec
> > >      2,943,676,361      cycles:u                  #    2.904 GHz
> > >        346,607,769      cycles:k                  #    0.342 GHz
> > >      8,464,188,379      instructions:u            #    2.88  insn per cycle
> > >        226,665,530      instructions:k            #    0.65  insn per cycle
> > 
> > This is quite compelling.
> > 
> > If you don't mind I can get this pushed soon in the next couple of days
> > -- or do you want to do it yourself?
> 
> I was thinking of pushing the attached, to both 14 and master, thinking
> that was what you meant, but then I wasn't quite sure: It's a relatively
> minor performance improvement, after all? OTOH, it arguably also just is
> a bit of an API misuse...
> 
> I'm inclined to push it to 14 and master, but ...

RMT: ^

Greetings,

Andres Freund