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Message-ID: <4b09a0c0506281147bc4b27f@mail.gmail.com>
Date: Tue, 28 Jun 2005 20:47:27 +0200
From: Jean-Max Reymond <jmreymond@gmail.com>
Reply-To: Jean-Max Reymond <jmreymond@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Re: perl garbage collector
In-Reply-To: <11126.1119938006@sss.pgh.pa.us>
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References: <4b09a0c050627134660b3925@mail.gmail.com>
	<11126.1119938006@sss.pgh.pa.us>

2005/6/28, Tom Lane <tgl@sss.pgh.pa.us>:
> Jean-Max Reymond <jmreymond@gmail.com> writes:
> > I have a stored procedure written in perl and I doubt that perl's
> > garbage collector is working :-(
> > after a lot of work, postmaster has a size of 1100 Mb and  I think
> > that the keyword "undef" has no effects.
>=20
> Check the PG list archives --- there's been previous discussion of
> similar issues.  I think we concluded that when Perl is built to use
> its own private memory allocator, the results of that competing with
> malloc are not very pretty :-(.  You end up with a fragmented memory
> map and no chance to give anything back to the OS.

thanks Tom for your advice. I have read the discussion but a small
test is very confusing for me.
Consider this function:

CREATE FUNCTION jmax() RETURNS integer
    AS $_$use strict;

my $i=3D0;
for ($i=3D0; $i<10000;$i++) {
        my $ch =3D "0123456789"x100000;
        my $res =3D spi_exec_query("select * from xdb_child where
doc_id=3D100 and ele_id=3D3 ");
}
my $j=3D1;$_$
    LANGUAGE plperlu SECURITY DEFINER;


ALTER FUNCTION public.jmax() OWNER TO postgres;

the line my $ch =3D "0123456789"x100000;   is used to allocate 1Mb.
the line my $res =3D spi_exec_query("select * from xdb_child where
doc_id=3D100 and ele_id=3D3 limit 5"); simulates a query.

without spi_exec_quer, the used memory in postmaster is a constant.
So, I think that pl/perl manages correctly memory in this case.
with spi_exec_query, postmaster grows and grows until the end of the loop.=
=20
Si, it seems that spi_exec_query does not release all the memory after
each call.
For my application (in real life) afer millions of spi_exec_query, it
grows up to 1Gb :-(


--=20
Jean-Max Reymond
CKR Solutions Open Source
Nice France
http://www.ckr-solutions.com