Re: PostgreSQL strugling during high load

From: Mindaugas Riauba
Subject: Re: PostgreSQL strugling during high load
Date: ,
Msg-id: 022901c557c5$73df1220$f20214ac@bite.lt
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In response to: PostgreSQL strugling during high load  ("Mindaugas Riauba")
Responses: Re: PostgreSQL strugling during high load  (Tom Lane)
Re: PostgreSQL strugling during high load  (Cosimo Streppone)
Re: PostgreSQL strugling during high load  ("Matthew T. O'Connor")
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PostgreSQL strugling during high load  ("Mindaugas Riauba", )
 Re: PostgreSQL strugling during high load  ("Steinar H. Gunderson", )
 Re: PostgreSQL strugling during high load  (Tom Lane, )
  Re: PostgreSQL strugling during high load  (Mischa Sandberg, )
 Re: PostgreSQL strugling during high load  ("Mindaugas Riauba", )
  Re: PostgreSQL strugling during high load  (Tom Lane, )
   Re: PostgreSQL strugling during high load  (Donald Courtney, )
  Re: PostgreSQL strugling during high load  (Cosimo Streppone, )
  Re: PostgreSQL strugling during high load  ("Matthew T. O'Connor", )
   Re: PostgreSQL strugling during high load  ("Thomas F. O'Connell", )
 Re: PostgreSQL strugling during high load  ("Mindaugas Riauba", )
  Re: PostgreSQL strugling during high load  ("Steinar H. Gunderson", )
 Re: PostgreSQL strugling during high load  ("Mindaugas Riauba", )
  Re: PostgreSQL strugling during high load  (Tom Lane, )
 Re: PostgreSQL strugling during high load  ("Mindaugas Riauba", )
 Re: PostgreSQL strugling during high load  ("Anjan Dave", )
  Re: PostgreSQL strugling during high load  (Donald Courtney, )
  Re: PostgreSQL strugling during high load  (Vivek Khera, )
  Re: PostgreSQL strugling during high load  (Josh Berkus, )
   Re: PostgreSQL strugling during high load  (Steve Poe, )
 Re: PostgreSQL strugling during high load  ("Anjan Dave", )

> > ... So contents of database changes very fast. Problem is that when
> > pg_autovacuum does vacuum those changes slows down too much.
>
> The "vacuum cost" parameters can be adjusted to make vacuums fired
> by pg_autovacuum less of a burden.  I haven't got any specific numbers
> to suggest, but perhaps someone else does.

  It looks like that not only vacuum causes our problems. vacuum_cost
seems to lower vacuum impact but we are still noticing slow queries "storm".
We are logging queries that takes >2000ms to process.
  And there is quiet periods and then suddenly 30+ slow queries appears in
log within the same second. What else could cause such behaviour? WAL log
switch? One WAL file seems to last <1 minute.

  And also in slow queries log only function call is shown. Maybe it is
possible
to get exact query which slows everything down in the serverlog?

  Thanks,

  Mindaugas



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