Re: Strange performance response for high load times

От: Kevin Grittner
Тема: Re: Strange performance response for high load times
Дата: ,
Msg-id: 4A3A64CD0200002500027DB9@gw.wicourts.gov
(см: обсуждение, исходный текст)
Ответ на: Re: Strange performance response for high load times  (Peter Alban)
Список: pgsql-performance

Скрыть дерево обсуждения

Strange performance response for high load times  (Peter Alban, )
 Re: Strange performance response for high load times  (Kenneth Marshall, )
  Re: Strange performance response for high load times  (Peter Alban, )
   Re: Strange performance response for high load times  (Kenneth Marshall, )
    Re: Strange performance response for high load times  (Peter Alban, )
     Re: Strange performance response for high load times  ("Kevin Grittner", )

Peter Alban <> wrote:

> Why is there such a big difference ?
>
> i.e. off peek times a simple select with where (on indexed column)
> and limit taks* 40 ms* during peek times it took *2 seconds*  - 50
> times slower !

If your high work_mem setting you may have been causing the OS to
discard cached data, causing disk reads where you normally get cache
hits, or even triggered swapping.  Either of those can easily cause a
difference of that magnitude, or more.

-Kevin


В списке pgsql-performance по дате сообщения:

От: "Kevin Grittner"
Дата:
Сообщение: Re: select max() much slower than select min()
От: Kenneth Marshall
Дата:
Сообщение: Re: 8.4 COPY performance regression on Solaris