Re: general PG network slowness (possible cure) (repost)
От | Bruce Momjian |
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Тема | Re: general PG network slowness (possible cure) (repost) |
Дата | |
Msg-id | 200705282108.l4SL8ED06035@momjian.us обсуждение исходный текст |
Ответ на | Re: general PG network slowness (possible cure) (repost) ("Peter T. Breuer" <ptb@inv.it.uc3m.es>) |
Список | pgsql-performance |
Please let us know if there is something we should change in the PostgreSQL source code. --------------------------------------------------------------------------- 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 > > ---------------------------(end of broadcast)--------------------------- > TIP 7: You can help support the PostgreSQL project by donating at > > http://www.postgresql.org/about/donate -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
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