On Wed 02 Oct 2002 22:11, Michael G Schwern <[EMAIL PROTECTED]> wrote:
> On Wed, Oct 02, 2002 at 01:50:56PM +0200, H.Merijn Brand wrote:
> > SYNOPSIS
> > use Devel::Internals;
>
> A little broad. Perhaps Devel::Memory?
My intent was to gather more internal states. Whatever useful.
> > my $end = sbrk ();
> >
> > my @array = (1..10000);
> > print "The creation of this array used ",
> > sbrk () - $end, "bytes\n";
> >
> > # Easier
> > use Devel::Internals;
> >
> > my @array = (1..10000);
> > MemUsed "creation of array";
> >
> > my @dup = @array;
> > MemUsed "duplication of array";
> >
> > DESCRIPTION
> > sbrk
> > returns the current memory top. See sbrk(2) manual page
>
> I realize that sbrk() is a familiar concept to deep C programmers on
> BSD-style systems, but in order for this to be useful to Perl programmers,
> or even users not familiar with BSD, you're going to have to name it
> something more descriptive than sbrk() and explain better what it does.
That's why there /is/ an Internals.pm: to hide the gory details and
implementation specifics to the user.
> It can still do the same thing as sbrk(), and you might even want to leave
> in an alias to sbrk() so BSD core hackers can feel all warm and fuzzy.
>
>
> > MemUsed ($msg)
> > Used in void context reports the number of bytes used since the
> > previous call to MemUsed with the message passed
>
> Global state is a Bad Thing. Consider when you have two different,
But having only /one/ interpeter, it *is* a global state. Nothing you can do
about it.
> unrelated subroutines both calling MemUsed() in the same program. foo()
> calls MemUsed() then bar() then foo() calls MemUsed() again expecting to get
> the memory used since it's last call but it's actually getting the memory
> used since bar() last called it.
Bad luck. we don't have any tool to separate.
> If you're going to keep state like this, better just have an object to
> represent various views on the memory state.
No way. This was meant to be a *low* level interface to help you find memory
hogs and other possible snakes. I see no use whatsoever in any production
environment. That's why I went for Devel:: namespace
> I can see two interfaces for this, possibly parallel. One is similar to
> your MemUsed() except the state is stored perl object. It simply returns
> the memory used since the last check on that object.
>
> package A;
> my $mem_state = Devel::Memory->new;
>
> sub foo {
> printf "%d has been used since the last call to foo()\n",
> $mem_state->used_since_last;
> }
>
> The other one allows you to more easily track the memory usage of a block of
> code by saying "track from this point to this point". Here's an example of
> tracking the memory used inside a subroutine.
>
> # meanwhile, in another file
> package B;
> my $mem_state = Devel::Memory->new;
>
> sub bar {
> $mem_state->start;
> ...do some stuff...
> printf "%d was used inside bar()\n", $mem_state->stop;
> }
>
> For convinence, stop() returns the amount of memory used so you can do it in
> two steps (start, stop/report) rather than three (start, stop, report).
>
> The other nice part about having an object is you can then hang lots of
> methods off it without polluting the caller's namespace. So you can have
> your methods which print neatly formatted diagnostics seperate from your
> methods which simply return values.
>
>
> > Used in scalar context returns the current sbrk value
>
> Shouldn't sbrk() do that? Is this the same value as MemUsed() would print
> in void context?
Complaints enough already about sbrk (). MemUsed () should hide the
implementation. That's why.
MemUsed ("blah"); # void context
should print a message to STDERR
while
my $mem = MemUsed ("now"); # Scalar context
should print nothing, but return the sbrk value, hiding the sbrk call to the
user, but still putting it on the history stack.
> > Used in list context returns the values saved on every call
>
> ?
See another answer in this thread proposing to return a list of lists. I like
that.
--
H.Merijn Brand Amsterdam Perl Mongers (http://amsterdam.pm.org/)
using perl-5.6.1, 5.8.0 & 633 on HP-UX 10.20 & 11.00, AIX 4.2, AIX 4.3,
WinNT 4, Win2K pro & WinCE 2.11. Smoking perl CORE: [EMAIL PROTECTED]
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