Re: Problems with autovacuum

From: Tom Lane
Subject: Re: Problems with autovacuum
Date: ,
Msg-id: 21508.1243380434@sss.pgh.pa.us
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In response to: Re: Problems with autovacuum  (Alvaro Herrera)
Responses: Re: Problems with autovacuum  (Alvaro Herrera)
List: pgsql-performance

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Problems with autovacuum  (Łukasz Jagiełło, )
 Re: Problems with autovacuum  (Scott Marlowe, )
  Re: Problems with autovacuum  (Grzegorz Jaśkiewicz, )
   Re: Problems with autovacuum  (Scott Marlowe, )
   Re: Problems with autovacuum  (Łukasz Jagiełło, )
    Re: Problems with autovacuum  (Tom Lane, )
     Re: Problems with autovacuum  (Łukasz Jagiełło, )
     Re: Problems with autovacuum  (Alvaro Herrera, )
      Re: Problems with autovacuum  (Tom Lane, )
       Re: Problems with autovacuum  (Alvaro Herrera, )
        Re: Problems with autovacuum  (Tom Lane, )
         Re: Problems with autovacuum  (Alvaro Herrera, )
          Re: Problems with autovacuum  (Tom Lane, )
           Re: Problems with autovacuum  (Alvaro Herrera, )
            Re: Problems with autovacuum  (Tom Lane, )
             Re: Problems with autovacuum  (Scott Marlowe, )
             Re: Problems with autovacuum  (Alvaro Herrera, )
              Re: Problems with autovacuum  (Tom Lane, )
               Re: Problems with autovacuum  (Alvaro Herrera, )
                Re: Problems with autovacuum  (Alvaro Herrera, )
                Re: Problems with autovacuum  (Tom Lane, )
       Re: Problems with autovacuum  (Łukasz Jagiełło, )
  Re: Problems with autovacuum  (Łukasz Jagiełło, )
   Re: Problems with autovacuum  (Grzegorz Jaśkiewicz, )

Alvaro Herrera <> writes:
> Tom Lane escribi�:
>> Hmm, maybe we need to improve the code too.  This example suggests that
>> there needs to be some limit on the worker launch rate, even if there
>> are so many databases that that means we don't meet naptime exactly.

> We already have a 100ms lower bound on the sleep time (see
> launcher_determine_sleep()).  Maybe that needs to be increased?

Maybe.  I hesitate to suggest a GUC variable ;-)

One thought is that I don't trust the code implementing the minimum
too much:

    /* 100ms is the smallest time we'll allow the launcher to sleep */
    if (nap->tv_sec <= 0 && nap->tv_usec <= 100000)
    {
        nap->tv_sec = 0;
        nap->tv_usec = 100000;    /* 100 ms */
    }

What would happen if tv_sec is negative and tv_usec is say 500000?
Maybe negative tv_sec is impossible here, but ...

            regards, tom lane


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