Re: [BUGS] BUG #9223: plperlu result memory leak - Mailing list pgsql-hackers

Hello, All!

eshkinkot@gmail.com writes:

> create function perl_test(IN data text, OUT v1 text, OUT v2 integer, OUT v3
> integer, OUT v4 json, OUT v5 json)
>   returns record as
> $BODY$
>
> use strict;
> use warnings;
>
> my $res->{'v1'} = 'content';
>
> return $res;
>
> $BODY$
>   language plperlu volatile strict;

> test case:
> select count(perl_test('')) from generate_series(1, 1000000);

It looks like I found the problem, Perl use reference count and something that
is called "Mortal" for memory management.  As I understand it, mortal is free
after FREETMPS. Plperl call FREETMPS in plperl_call_perl_func() but after it,
plperl ask perl interpreter again for new mortal SV variables, for example, in
hek2cstr from plperl_sv_to_datum, and this new SV is newer freed.

I experiment with this patch, and it fix memory leak in my case, but patch
is incomplete. It does not free on error and fix only plperl_func_handler,
plperl_trigger_handler and may be plperl_inline_handler must be also fixed.

Patch for REL9_2_STABLE.

without patch:
  PID    VSZ   RSS
 2503  74112  7740
 2503 152928 86860
 2503 232208 165836
 2503 310732 244508
 2503 389264 323032

with patch:
  PID    VSZ   RSS
 4322  74112  7740
 4322  74380  8340
 4322  74380  8340
 4322  74380  8340
 4322  74380  8340


diff --git a/src/pl/plperl/plperl.c b/src/pl/plperl/plperl.c
index 49d50c4..9c9874d 100644
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -2173,6 +2173,9 @@ plperl_func_handler(PG_FUNCTION_ARGS)
     ReturnSetInfo *rsi;
     ErrorContextCallback pl_error_context;

+    ENTER;
+    SAVETMPS;
+
     if (SPI_connect() != SPI_OK_CONNECT)
         elog(ERROR, "could not connect to SPI manager");

@@ -2271,6 +2274,9 @@ plperl_func_handler(PG_FUNCTION_ARGS)

     SvREFCNT_dec(perlret);

+    FREETMPS;
+    LEAVE;
+
     return retval;
 }