Re: linux deadline i/o elevator tuning

От: Kevin Grittner
Тема: Re: linux deadline i/o elevator tuning
Дата: ,
Msg-id: 49DDC286.EE98.0025.0@wicourts.gov
(см: обсуждение, исходный текст)
Ответ на: Re: linux deadline i/o elevator tuning  (Matthew Wakeling)
Список: pgsql-performance

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linux deadline i/o elevator tuning  (Mark Wong, )
 Re: linux deadline i/o elevator tuning  ("Kevin Grittner", )
  Re: linux deadline i/o elevator tuning  (Grzegorz Jaśkiewicz, )
   Re: linux deadline i/o elevator tuning  (Matthew Wakeling, )
    Re: linux deadline i/o elevator tuning  (Grzegorz Jaśkiewicz, )
     Re: linux deadline i/o elevator tuning  ("Kevin Grittner", )
      Re: linux deadline i/o elevator tuning  (Grzegorz Jaśkiewicz, )
     Re: linux deadline i/o elevator tuning  (Matthew Wakeling, )
    Re: linux deadline i/o elevator tuning  ("Kevin Grittner", )
   Re: linux deadline i/o elevator tuning  (Scott Carey, )
   Re: linux deadline i/o elevator tuning  ("Albe Laurenz *EXTERN*", )
    Re: linux deadline i/o elevator tuning  (Jeff, )
     Re: linux deadline i/o elevator tuning  ("Kevin Grittner", )
  Re: linux deadline i/o elevator tuning  (Arjen van der Meijden, )
   Re: linux deadline i/o elevator tuning  ("Kevin Grittner", )
 Re: linux deadline i/o elevator tuning  (Mark Wong, )
  Re: linux deadline i/o elevator tuning  (Mark Wong, )

Matthew Wakeling <> wrote:
> On Thu, 9 Apr 2009, Grzegorz Jaœkiewicz wrote:
>> acording to kernel folks, anticipatory scheduler is even better for
>> dbs.  Oh well, it probably means everyone has to test it on their
>> own at the end of day.
>
> But the anticipatory scheduler basically makes the huge assumption
> that you have one single disc in the system that takes a long time
> to seek from one place to another. This assumption fails on both
> RAID arrays and SSDs, so I'd be interested to see some numbers to
> back that one up.

Yeah, we're running on servers with at least 4 effective spindles,
with some servers having several dozen effective spindles.  Assuming
one is not very effective.  The setting which seemed sluggish for our
environment was the anticipatory scheduler, so the kernel guys
apparently aren't thinking about the type of load we have on the
hardware we have.

-Kevin


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