Luke Kenneth Casson Leighton lkcl at samba-tng.org
Tue Mar 6 09:44:58 GMT 2001

On Mon, 5 Mar 2001, Jeremy Allison wrote:

> On Tue, Mar 06, 2001 at 12:31:13AM +1100, Luke Kenneth Casson Leighton wrote:
> > when i described to dr andrew tridgell that i was adding a talloc_realloc,
> > i was informed that this makes the purpose of talloc - trivial alloc -
> > non-trivial.  therefore, the function is unacceptable.
> > 
> > now, jeremy adds talloc_realloc.
> > 
> > this implies that the rejection of the addition of this function was not
> > for technical reasons.
> I know I shouldn't answer this but......
> *I* added talloc_realloc to the 2.2 tree without consultation with
> Andrew in order to try and fix the same problem you describe.

i know.
> I eventually got it working (it was non-trivial) and after much
> testing (until 1am :-) discovered that when enumerating a 10,000
> printer job queue list it *still* used more than 20mb of virtual
> memory more than the less elegent realloc code (which I left working
> in head).

> Dishartened, I went home. That was over the weekend. As I'm working
> from home today on a white paper I didn't get chance to revert the 
> changes to 2.2 back to the code used in HEAD. I will be doing so
> tomorrow and that implementation of talloc_realloc will be history.
> So yes it *was* for technical reasons, you just need to be able to
> do the tests and determine this for yourself. Now the question remains,
> did *you* do those tests and remove it in your code, or did you just
> leave it in for the case you tested assuming it was ok for all cases ?

i used trealloc() only for the marshalling buffer memory, as using talloc
was utterly hammering memory.

so it was a very specific and limited usage: a tool - an optimisation -
for a job.

so, it was there for one specific case - not all cases.

if you are using talloc_realloc for general memory allocation, including
structures used by the function calls, then well yeah, you're going to get

ESPECIALLY with the printing code.  remember, the functions go like this:

spoolss_get_printer_data(1024, void*buffer, size_t **size_needed)

server: error_buff_to_small, size_needed = 1024000.

spoolss_get_printer_data(1024000, void *buffer)

but the client-side code in nt is so STUPID in places that it continues to
use the buffer size 1024000 even though the buffer _actuall_ required for
a particular structure may be only 1 byte.

have you considered using more than one TALLOC_CTX?

one for marshalling, one for unmarshalling, one for memory returned to
client-side usage, one for memory returned for server-side usage?

> This is why Andrew is the head of the Team, 'cos he can see these
> things without the pain I have to go through to see them :-) :-).

andrew has specific technical skills in specific areas.

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