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Re: REINDEX using only 1 CPU (of 2)

From: "Phillip Smith" <phillip(dot)smith(at)weatherbeeta(dot)com(dot)au>
To: <ogjunk-pgjedan(at)yahoo(dot)com>,<pgsql-admin(at)postgresql(dot)org>
Subject: Re: REINDEX using only 1 CPU (of 2)
Date: 2007-04-15 23:29:01
Message-ID: 007401c77fb5$d9886030$9b0014ac@wbaus090 (view raw or flat)
Thread:
Lists: pgsql-admin
A REINDEX is one process - you can't split one process over 2 CPU's.

If you start another process (a SELECT / UPDATE / INSERT for example), that
process (should) use the other processor.

Cheers,
~p


-----Original Message-----
From: pgsql-admin-owner(at)postgresql(dot)org
[mailto:pgsql-admin-owner(at)postgresql(dot)org] On Behalf Of
ogjunk-pgjedan(at)yahoo(dot)com
Sent: Saturday, 14 April 2007 10:55
To: pgsql-admin(at)postgresql(dot)org
Subject: [ADMIN] REINDEX using only 1 CPU (of 2)

Hi,

I've got PG 8.2.3 running on a dual-core P4, and I noticed that, at least
during reindexing, postgreSQL REINDEX process is using only 1 of those 2
cores.  You can clearly see this from this snippet from top:

Cpu0  : 93.3% us,  6.7% sy,  0.0% ni,  0.0% id,  0.0% wa,  0.0% hi,  0.0% si
Cpu1  :  0.0% us,  2.6% sy,  0.0% ni, 85.5% id, 11.8% wa,  0.0% hi,  0.0% si


  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND

21909 pg  25   0  116m  89m  42m R 98.9  9.2   1:01.92 postgres: pg mydb
[local] REINDEX



This PG 8.2.3 was compiled from sources on this box, so if there is anything
in the config/install process that should pick up that this box has "2"
CPUs, perhaps that didn't happen?  I know I didn't manually instruct the
config/install that the box is a dual-core box.  This is running on a Linux
box with the SMP-aware kernel.

Is this a known limitation?  Am I reading this wrong?

Thanks,
Otis



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