Re: 7.4.6 FC2 MUCH slower from 2.6.9-1.11 to 2.6.10-1.8

On Sun, 20 Feb 2005 12:35:02 -0300 (ART), Clodoaldo Pinto
<clodoaldo_pinto@yahoo.com.br> wrote:
> I made the same experience now with PG 8.01, FC3 and 512MB memory. The previous
> was PG 7.4.6, FC2 and 1GB.
>
> The difference in performance between kernels 2.6.9-1.724 and 2.6.10-1.766 is
> still huge.
>
> I notice that in 2.6.10 the function accesses the disk much more.
>
> Does anyone know what changes from 2.6.9 to 2.6.10 could cause this drop in
> performance?
>
> Regards, Clodoaldo Pinto
>

This message did not connect to the original thread. So this is the reference:
http://archives.postgresql.org/pgsql-general/2005-01/msg00569.php

> 31 minutes in 2.6.10-1.8:
>
> select kstime(), update_ranking_usuarios(), kstime();
>        kstime        | update_ranking_usuarios |       kstime
> ---------------------+-------------------------+---------------------
>  2005-01-13 20:27:56 |                         | 2005-01-13 20:58:46
> (1 row)
>
> 5 minutes in 2.6.9-1.11:
>
> select kstime(), update_ranking_usuarios(), kstime();
>        kstime        | update_ranking_usuarios |       kstime
> ---------------------+-------------------------+---------------------
>  2005-01-13 23:24:30 |                         | 2005-01-13 23:29:26
> (1 row)
>
> The function:
>
> CREATE OR REPLACE FUNCTION update_ranking_usuarios()
>   RETURNS void AS
> 'declare
>  linha record;
>  rank integer;
> begin
> rank := 0;
> for linha in
>  select usuario
>   from usuarios_producao
>   where not anonymous --and n_time != 446
>   order by pontos_0 desc
> loop
>  rank := rank + 1;
>  update usuarios_producao
>   set rank_0 = rank
>   where usuario = linha.usuario
>   ;
> end loop;
> -- ----------------------------------------------------------
> rank := 0;
> for linha in
>  select usuario
>   from usuarios_producao
>   where not anonymous --and n_time != 446
>   order by pontos_0 + (( pontos_0 - pontos_7) / 7) desc
> loop
>  rank := rank + 1;
>  update usuarios_producao
>   set rank_24 = rank
>   where usuario = linha.usuario
>   ;
> end loop;
> -- ----------------------------------------------------------
> rank := 0;
> for linha in
>  select usuario
>   from usuarios_producao
>   where not anonymous --and n_time != 446
>   order by pontos_0 + pontos_0 - pontos_7 desc
> loop
>  rank := rank + 1;
>  update usuarios_producao
>   set rank_7 = rank
>   where usuario = linha.usuario
>   ;
> end loop;
> -- ----------------------------------------------------------
> rank := 0;
> for linha in
>  select usuario
>   from usuarios_producao
>   where not anonymous --and n_time != 446
>   order by pontos_0 + (( pontos_0 - pontos_7) * 30 / 7) desc
> loop
>  rank := rank + 1;
>  update usuarios_producao
>   set rank_30 = rank
>   where usuario = linha.usuario
>   ;
> end loop;
> return;
> end;'
>   LANGUAGE 'plpgsql' STABLE;
>
> Part of postgresql.conf:
>
> shared_buffers = 3000           # min 16, at least max_connections*2, 8KB
> each
> sort_mem = 49152                # min 64, size in KB
> vacuum_mem = 32768              # min 1024, size in KB
> vacuum_mem = 32768
> max_fsm_pages = 300000          # min max_fsm_relations*16, 6 bytes each
> fsync = false
> wal_buffers = 256
> checkpoint_segments = 32        # in logfile segments, min 1, 16MB each
>
> The log file shows only a long list of:
>
> LOG:  recycled transaction log file "0000010A000000D0"
> LOG:  recycled transaction log file "0000010A000000CF"
> LOG:  recycled transaction log file "0000010A000000C9"
> ...
>
> Regards, Clodoaldo Pinto
>