Tim,
I'm experiencing further memory leaks which are causing me more grief. I put
together the following test script which illustrates the leakage:
#/usr/bin/perl
# dbi.pl
use DBI;
use Devel::Leak;
my $leak_handle;
for ( 1 .. 1000 ) {
my $dbh = DBI->connect("DBI:mysql:MYDB","user","secret", {RaiseError=>1});
my $sth = $dbh->prepare("SELECT COUNT(*) FROM TABLE");
$sth->execute();
while ( my ($c) = $sth->fetchrow_array() ) {
# print "$c\n";
}
$sth->finish;
$dbh->disconnect;
system("ps -aux | fgrep dbi.pl | fgrep -v fgrep");
test_leak();
}
sub test_leak {
if ( $handle ) {
Devel::Leak::CheckSV($handle);
}
print STDERR "count: " . Devel::Leak::NoteSV($handle) . "\n";
}
Devel::Leak shows that it is leaking 4 "things" every iteration:
count: 12128
root 17720 17.8 0.3 6840 4220 pts/0 S 09:55 0:00 perl dbi.pl
new 0x8aad3e8 : SV = PVHV(0x8a68b30) at 0x8aad3e8
REFCNT = 1
FLAGS = (PADBUSY,PADMY,SHAREKEYS)
IV = 0
NV = 0
ARRAY = 0x0
KEYS = 0
FILL = 0
MAX = 7
RITER = -1
EITER = 0x0
new 0x8aad3f4 : SV = NULL(0x0) at 0x8aad3f4
REFCNT = 1
FLAGS = (PADBUSY,PADMY)
new 0x8aad400 : SV = NULL(0x0) at 0x8aad400
REFCNT = 1
FLAGS = (PADBUSY,PADMY)
new 0x8aad40c : SV = NULL(0x0) at 0x8aad40c
REFCNT = 1
FLAGS = (PADBUSY,PADMY)
count: 12132
I think there might be several leaks here. If I move the connect() out of the
loop, it's leaking, but less - just one of those NULL SV guys.
Can you please help me track this down? I'm still a little scared of the
DBI.xs internals, despite my recent exposure...
Thanks a lot,
edan
> -----Original Message-----
> From: Tim Bunce [mailto:[EMAIL PROTECTED]
> Sent: Monday, July 03, 2006 12:16
> To: Ephraim Dan
> Cc: Tim Bunce; dbi-users@perl.org
> Subject: Re: memory leak in DBI XS bootstrap code
>
> On Sat, Jul 01, 2006 at 10:42:58PM -0700, Ephraim Dan wrote:
> > Thanks for the help Tim! You've really done me a great service.
> >
> > I have created the following patch, which appears to fix all of the
> leaks. Can you please review it, and give it your stamp of approval? I
> am willing to use this patch if you approve it, until a new DBI is
> available with the fixes.
>
> Looks okay at first sight, except that Newz returns memory that's been
> reset to zero bytes. You need to add the memzero I suggested previously.
> Might as well go into malloc_using_sv since it's not performance critical.
>
> Um, looks like CLONE plus _clone_dbis plus dbi_bootinit already do the
> right thing (your patch also fixes a leak on thread creation) so that's
> okay. INIT_PERINTERP is harder to be sure about, but I think it's okay.
>
> I'll apply the patch and add the memzero. Thanks edan.
>
> Tim.
>
> > Thanks again,
> > edan
> >
> > The patch:
> >
> > --- DBI.xs.orig 2006-06-30 10:20:10.000000000 -0400
> > +++ DBI.xs 2006-07-02 04:59:32.000000000 -0400
> > @@ -171,7 +171,7 @@
> > dPERINTERP_SV; dPERINTERP_PTR(PERINTERP_t *, PERINTERP)
> > # define INIT_PERINTERP \
> > dPERINTERP; \
> > - Newz(0,PERINTERP,1,PERINTERP_t); \
> > + PERINTERP = malloc_using_sv(sizeof(PERINTERP_t)); \
> > sv_setiv(perinterp_sv, PTR2IV(PERINTERP))
> >
> > # undef DBIS
> > @@ -209,13 +209,29 @@
> > stc_s, sizeof(dbih_stc_t), fdc_s, sizeof(dbih_fdc_t),
> msg);
> > }
> >
> > +static void *
> > +malloc_using_sv(STRLEN len)
> > +{
> > + dTHX;
> > + SV *sv = newSV(len);
> > + return SvPVX(sv);
> > +}
> > +
> > +static char *
> > +savepv_using_sv(char *str)
> > +{
> > + char *buf = malloc_using_sv(strlen(str));
> > + strcpy(buf, str);
> > + return buf;
> > +}
> > +
> > static void
> > dbi_bootinit(dbistate_t * parent_dbis)
> > {
> > dTHX;
> > INIT_PERINTERP;
> >
> > - Newz(dummy, DBIS, 1, dbistate_t);
> > + DBIS = (struct dbistate_st*)malloc_using_sv(sizeof(struct
> dbistate_st));
> >
> > /* store version and size so we can spot DBI/DBD version mismatch
> */
> > DBIS->check_version = check_version;
> > @@ -3793,7 +3809,7 @@
> > ima->minargs = (U8)SvIV(*av_fetch(av, 0, 1));
> > ima->maxargs = (U8)SvIV(*av_fetch(av, 1, 1));
> > svp = av_fetch(av, 2, 0);
> > - ima->usage_msg = savepv( (svp) ? SvPV(*svp,lna) : "");
> > + ima->usage_msg = (svp) ? savepv_using_sv(SvPV(*svp, lna)) :
> "";
> > ima->flags |= IMA_HAS_USAGE;
> > if (trace_msg && DBIS_TRACE_LEVEL >= 11)
> > sv_catpvf(trace_msg, ",\n usage: min %d, max %d,
> '%s'",
> >
> > > -----Original Message-----
> > > From: Tim Bunce [mailto:[EMAIL PROTECTED]
> > > Sent: Friday, June 30, 2006 16:33
> > > To: Ephraim Dan
> > > Cc: Tim Bunce; dbi-users@perl.org
> > > Subject: Re: memory leak in DBI XS bootstrap code
> > >
> > > On Fri, Jun 30, 2006 at 04:08:46AM -0700, Ephraim Dan wrote:
> > > > This is why I love the perl community - you're willing to help
> even
> > > though you don't have time, since
> > > > you care about your code, and that other people can benefit from
> it.
> > > >
> > > > But ... you sort of left a dangling "But" in your last post. Do
> you
> > > have a suggestion to fix the
> > > > _install_method problem?
> > > >
> > > > I just ran valgrind with your fix - there seems to still be a
> leak.
> > > It is reported on DBI.xs line 216:
> > > > INIT_PERINTERP;
> > > > That looks to also have a Newz in it - is that what leaks?
> > >
> > > Yes. It's basically a plain malloc and there's no mechanism to free it
> > > later.
> > >
> > > > Can you suggest how to fix that one?
> > >
> > > The trick is to use newSV to alloc memory in the form of an SV
> > > so that when the interpreter is destroyed the SV memory gets freed
> > > automatically.
> > >
> > > > The _install_method leak is reported on line 3800 (in my modified
> > > DBI.xs) which validates your theory:
> > > > ima->usage_msg = savepv( (svp) ? SvPV(*svp,lna) : "");
> > > > If you can fix these, I'll be forever in your debt...
> > >
> > > As above, and as outlined previously, use an SV.
> > > Something like this (completely untested):
> > >
> > > static void *
> > > malloc_using_sv(STRLEN len) {
> > > SV *sv = newSV(len);
> > > return SvPVX(sv);
> > > }
> > >
> > > static char *
> > > savepv_using_sv(char *str) {
> > > char *buf = malloc_using_sv(strlen(str));
> > > strcpy(buf, str);
> > > return buf;
> > > }
> > >
> > > Tim.
> > >
> > > > --edan
> > > >
> > > > -----------------------------------------------------------------
> ----
> > > -----------------------------------
> > > >
> > > > From: Tim Bunce [mailto:[EMAIL PROTECTED]
> > > > Sent: Fri 6/30/2006 11:35
> > > > To: Ephraim Dan
> > > > Cc: Tim Bunce; dbi-users@perl.org
> > > > Subject: Re: memory leak in DBI XS bootstrap code
> > > >
> > > > On Fri, Jun 30, 2006 at 12:24:33AM -0700, Ephraim Dan wrote:
> > > > > > > I don't see what you mean in the "INSTALL" that comes with
> perl
> > > 5.8.0 (that's what we're using).
> > > > > > The file called INSTALL in the perl source code directory.
> > > > >
> > > > > That I knew. What are the special instructions that I'm
> supposed
> > > to
> > > > > find there? Am I supposed to build it with debugging? Can you
> > > > > specify what special configuration exactly you meant that I
> should
> > > use?
> > > >
> > > > I'm sorry. I should have checked myself first. You can build perl
> > > with
> > > > -DPURIFY to enable more precise leak detection.
> > > >
> > > > > It looks like the leak in boot_DBI is on purpose:
> > > > > /* Remember the last handle used. BEWARE! Sneaky stuff
> here!
> > > */
> > > > > /* We want a handle reference but we don't want to
> increment
> > > */
> > > > > /* the handle's reference count and we don't want perl to
> try
> > > */
> > > > > /* to destroy it during global destruction. Take care!
> > > */
> > > > > DBI_UNSET_LAST_HANDLE; /* ensure setup the correct way
> > > */
> > > > >
> > > > > Why is this being done, and does anyone have a way to fix it?
> Why
> > > don't we want perl to destroy it?
> > > > Me, that's exactly what I want.
> > > >
> > > > I don't believe that's a leak. It's just using an SV as a
> reference
> > > > without telling perl its a reference. If perl knew it was a
> reference
> > > > we'd get double-free warnings as the referenced value would be
> freed
> > > twice.
> > > >
> > > > The leak is probably the DBIS structure itself:
> > > >
> > > > Newz(dummy, DBIS, 1, dbistate_t);
> > > >
> > > > That should probably be using along the lines of:
> > > >
> > > > sv = newSV(sizeof(struct dbistate_st));
> > > > DBIS = (struct dbistate_st*)SvPVX(sv);
> > > > memzero(DBIS, sizeof(struct dbistate_st));
> > > >
> > > > So the memory is allocated within an SV so gets freed on global
> > > destruction.
> > > >
> > > > > Still looking into the other leak in _install_method... any
> > > pointers still appreciated... Thanks for
> > > > your help so far, Tim.
> > > >
> > > > I've taken a look at the code. I'd guess that it's due to
> savepnv:
> > > >
> > > > ima->usage_msg = savepv( (svp) ? SvPV(*svp,lna) : "");
> > > >
> > > > But
> > > >
> > > > Tim.
> > > >
> > > > > -edan
> > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Tim Bunce [[1]mailto:[EMAIL PROTECTED]
> > > > > > > Sent: Thursday, June 29, 2006 14:47
> > > > > > > To: Ephraim Dan
> > > > > > > Cc: dbi-users@perl.org
> > > > > > > Subject: Re: memory leak in DBI XS bootstrap code
> > > > > > >
> > > > > > > Try building perl with options to make valgrind leak
> tracing
> > > more
> > > > > > > effective (see perl's INSTALL file). That may help you
> pinpoint
> > > > > > > the problem.
> > > > > > >
> > > > > > > Tim.
> > > > > > >
> > > > > > > On Thu, Jun 29, 2006 at 04:33:40AM -0700, Ephraim Dan
> wrote:
> > > > > > > > I am experiencing what I believe to be a memory leak in
> the
> > > DBI
> > > > > > > bootstrap code. This is a problem for me because I am
> > > embedding perl in a
> > > > > > > long-running program, and DBI is being loaded over and
> over, so
> > > my program
> > > > > > > grows and grows.
> > > > > > > >
> > > > > > > > The problem appears to be in the following routines:
> > > > > > > >
> > > > > > > > boot_DBI (in /usr/lib/perl5/vendor_perl/5.8.0/i386-linux-
> > > thread-
> > > > > > > multi/auto/DBI/DBI.so)
> > > > > > > > XS_DBI__install_method (in
> > > /usr/lib/perl5/vendor_perl/5.8.0/i386-linux-
> > > > > > > thread-multi/auto/DBI/DBI.so)
> > > > > > > >
> > > > > > > > I am using DBI 1.51
> > > > > > > >
> > > > > > > > The tool "valgrind" ([2]http://valgrind.org
> > > <[3]http://valgrind.org/> ) can be used to reproduce
> > > > the
> > > > > > > leak using the following code:
> > > > > > > >
> > > > > > > > ---
> > > > > > > > File: embed_test.c
> > > > > > > > ---
> > > > > > > >
> > > > > > > > #include <EXTERN.h> /* from the Perl
> > > distribution */
> > > > > > > > #include <perl.h> /* from the Perl
> > > distribution */
> > > > > > > >
> > > > > > > > static PerlInterpreter *my_perl; /*** The Perl
> > > interpreter ***/
> > > > > > > > EXTERN_C void xs_init (pTHX); /*** init dyn.
> loading
> > > ***/
> > > > > > > >
> > > > > > > > int main(int argc, char **argv, char **env)
> > > > > > > > {
> > > > > > > > char *embedding[] = { "", "-e", "0" };
> > > > > > > > my_perl = perl_alloc();
> > > > > > > > perl_construct(my_perl);
> > > > > > > > perl_parse(my_perl, xs_init, 3, embedding, (char
> > > **)NULL);
> > > > > > > > PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
> > > > > > > > perl_run(my_perl);
> > > > > > > > eval_pv("use DBI", TRUE);
> > > > > > > > perl_destruct(my_perl);
> > > > > > > > perl_free(my_perl);
> > > > > > > > }
> > > > > > > >
> > > > > > > > ---
> > > > > > > > File: Makefile
> > > > > > > > ---
> > > > > > > >
> > > > > > > > CC_OPTS = $(shell perl -MExtUtils::Embed -e ccopts)
> > > > > > > > LD_OPTS = $(shell perl -MExtUtils::Embed -e ldopts)
> > > > > > > >
> > > > > > > > EXE = embed_test
> > > > > > > >
> > > > > > > > $(EXE): xsinit.o embed_test.o
> > > > > > > > gcc -o $(EXE) embed_test.o xsinit.o $(LD_OPTS)
> > > > > > > >
> > > > > > > > embed_test.o: embed_test.c
> > > > > > > > gcc -c embed_test.c $(CC_OPTS)
> > > > > > > >
> > > > > > > > xsinit.o: xsinit.c
> > > > > > > > gcc -c xsinit.c $(CC_OPTS)
> > > > > > > >
> > > > > > > > xsinit.c:
> > > > > > > > perl -MExtUtils::Embed -e xsinit -- -o xsinit.c
> > > > > > > >
> > > > > > > > clean:
> > > > > > > > rm -f *.o xsinit.c $(EXE)
> > > > > > > >
> > > > > > > > ---
> > > > > > > > EOF
> > > > > > > > ---
> > > > > > > >
> > > > > > > > Can anyone suggest a fix for this? I'd be more than
> willing
> > > to take a
> > > > > > > patch to DBI 1.51 as soon as someone has one.
> > > > > > > >
> > > > > > > > Thanks,
> > > > > > > > Ephraim Dan
> > > > > > > >
> > > > >
> > > >
> > > > References
> > > >
> > > > Visible links
> > > > 1. mailto:[EMAIL PROTECTED]
> > > > 2. http://valgrind.org/
> > > > 3. http://valgrind.org/
