in reply to Re: Memory efficiency, anonymous vs named's vs local subroutines
in thread Memory efficiency, anonymous vs named's vs local subroutines

The ca. 750 extra bytes for named subs may well be just the cost of allocating a GLOB for the subroutine in the symbol table,

Running the code below to create a million STASH aliases to a single sub:

sub F123456{  my( $a, $b, $c )= @_; my $x = 123456; return $a * $b - $
+c; };;
*{"X$_"} = \&F123456 for 0 .. 1e6;;

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results in an increase in the process size of almost exactly 300MB, thus 300 bytes per STASH entry.

Some of the extra space may be down to unreused (but reusable) space allocated and freed during the doubling of the STASH hash as it grows. I can't think of any way to isolate that.

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Re^3: Memory efficiency, anonymous vs named's vs local subroutines
by shmem (Chancellor) on Jul 19, 2015 at 07:21 UTC
    Some of the extra space may be down to unreused (but reusable) space allocated and freed during the doubling of the STASH hash as it grows.

    Devel::Peek shows that stash entries created by coderef assignment to a GLOB are missing the MAGIC part of a GV: 

    use Devel::Peek;
sub foo {
    print "in foo\n";
}
*bar = \&foo;
print "----\nfoo:\n----\n";
Dump(*foo);
print "----\nbar\n----\n";
Dump(*bar);
__END__
----
foo:
----
SV = PVGV(0x1765790) at 0x1731550
  REFCNT = 3
  FLAGS = (RMG,MULTI,IN_PAD)
  MAGIC = 0x1732e80
    MG_VIRTUAL = &PL_vtbl_backref
    MG_TYPE = PERL_MAGIC_backref(<)
    MG_OBJ = 0x1725238
  NAME = "foo"
  NAMELEN = 3
  GvSTASH = 0x1705800   "main"
  GP = 0x1732870
    SV = 0x0
    REFCNT = 1
    IO = 0x0
    FORM = 0x0  
    AV = 0x0
    HV = 0x0
    CV = 0x1725238
    CVGEN = 0x0
    LINE = 4
    FILE = "f.pl"
    FLAGS = 0xa
    EGV = 0x1731550     "foo"
----
bar
----
SV = PVGV(0x17657c0) at 0x1725208
  REFCNT = 3
  FLAGS = (MULTI,ASSUMECV,IN_PAD)
  NAME = "bar"
  NAMELEN = 3
  GvSTASH = 0x1705800   "main"
  GP = 0x1759a40
    SV = 0x0
    REFCNT = 1
    IO = 0x0
    FORM = 0x0  
    AV = 0x0
    HV = 0x0
    CV = 0x1725238
    CVGEN = 0x0
    LINE = 5
    FILE = "f.pl"
    FLAGS = 0xe
    EGV = 0x1725208     "bar"

    [download]

    I don't think the sizes reported by Devel::Size are accurate since the stash entry created by coderef assignment is reported as being bigger.
    Go figure.

    use Devel::Size qw(size total_size);
sub foo {
    print "in foo\n";
}
print "size foo: ",size(*foo),"\n";
print "total_size foo: ",total_size(*foo),"\n";
print "size bar: ",size(*bar),"\n";
print "total_size bar: ",total_size(*bar),"\n";
print "difference: ",size(*foo) - size(*bar),"\n";
__END__
size foo: 7034
total_size foo: 7034
size bar: 7186
total_size bar: 7186
difference: -152

    [download]
    perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'
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