Date: Tue, 20 Jul 2021 14:57:15 -0400
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org
Subject: Re: something is wonky with pgbench pipelining
Message-ID: <202107201857.kyv2gv3ouxot@alvherre.pgsql>
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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?

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"La espina, desde que nace, ya pincha" (Proverbio africano)