Re: general PG network slowness (possible cure) (repost)

Please let us know if there is something we should change in the
PostgreSQL source code.

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Peter T. Breuer wrote:
> "Also sprach Tom Lane:"
> > > It may still be useful. The kernel won't necessarily send data as you
> > > push it down to the network protocols and driver. The driver may decide
> > > to wait for more data to accumulate,
> >
> > No, because we set TCP_NODELAY. Once we've flushed a message to the
>
> That just means "disable Nagle", which is indeed more or less the
> correct thing to do .. you don't want to sit around waiting for more
> data when we're sure there will be none, as you say. Yet you also don't
> want to send short data out prematurely, which disabling Nagle can
> cause.
>
> And disabling Nagle doesn't actually force data out immediately you want
> it to be sent ... it just disables extra waits imposed by the Nagle
> algorithm/protocol. It doesn't stop the driver from waiting around
> because it feels taking the bus might be a bit premature right now,
> for example.
>
> > kernel, we don't want the kernel sitting on it --- any delay there adds
> > directly to the elapsed query time. At least this is the case for the
> > final response to a query. I'm not too clear on whether this means we
> > need to be careful about intermediate message boundaries when there's a
> > lot of data being sent.
>
> It's unclear. But not my situation.
>
>
> If I clear TCP_CORK all data is sent at that point. If I set TCP_CORK
> data is held until I clear TCP_CORK, or 200ms have passed with no send.
>
> Peter
>
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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
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