On Tue, Jan 22, 2013 at 7:57 AM, Cedric BAIL <[email protected]> wrote:
> Hello,
>
> I have been chasing source of memory consumption in EFL since a few
> weeks now. There is one source that I didn't hunt yet, callbacks. In
> some small elementary_test they easily get over 400KB of
> Evas_Func_Node. This func node are not that big, but they are still a
> list with a function pointer, two integer and a data pointer.
> When we look at our usage, in a lot of place, we do have the same
> pattern. We register a set of callbacks for always the same event with
> the function pointer and priority. The only thing that change is the
> data pointer.
> Instead of using a list, we could use an array, that would reduce
> our memory use, but still, not enough. Maybe overall, it wouldn't even
> b a win if we use an Eina_Inarray or an Eina_Array as they do require
> two additional integer, so the base structure when you have no
> callbacks will be bigger.
> So what we could do is provide an API to register a static const
> array of function pointer and event like an callback class. This
> pattern would match our use in Edje, Elementary and even Terminology.
> One "class" of callback per object, instead of n instance of callbacks
> per object. That should really reduce the memory we use for that.
> I don't want to push this new API in Evas, because we have that
> pattern with edje signal, smart callback and object callback. I think
> it should go to Eo and we should move our code to use such API.
>
> Any comments, though on that subject.
Given the nature of it, I guess it's easier to solve like:
evas_object_event_callback:
1 - dynamically allocate an array of pointers with size as the
number of elements in EVAS_CALLBACK_* enum: when unused, pointer-size
bytes. When used pointer-size * (elements-in-EVAS_CALLBACK_ + 1)
2 - for each callback, place in the aforementioned array another
inarray of pairs {cb, data}. You can avoid your extra integer cost for
inarray by implementing something manual, it won't hurt that much the
integer, but seems you're bugged about that. The size would be 2 *
pointer-size
right now we use 4 pointers per node (prev, next, cb, data), plus some
information that due alignment should take an extra pointer-size
(type, priority, delete_me). So 5 pointer-size at least, but on my
machine (32 bits) it's 28 bytes or 7 pointers.
We can avoid the 'deleted' bit by making cb = NULL in the structure.
If we use inarray (allocated size != used size), we can just swap
deleted elements to the end as well when we cleanup, avoiding
allocations at all. Problem is how to handle the priority part without
loosing much info, I'll count it as an extra-pointer-size.
Expected gains:
= empty =
now: 1 * pointer-size
new: 1 * pointer-size
= 1 event of 1 type =
now: 1 * pointer-size + 1 * (7 * pointer-size) = 8 * pointer-size
new: 1 * pointer-size + 34 * pointer-size + 1 * (3 * pointer-size) =
38 * pointer-size
= 10 events of 5 types (50 events) =
now: 1 * pointer-size + 50 * (7 * pointer-size) = 351 * pointer-size
new: 1 * pointer-size + 34 * pointer-size + 50 * (3 * pointer-size) =
185 * pointer-size
equation: 1 + N * 7 = 35 + N * 3; N * 7 - N * 3 = 35 - 1; N *
4 = 34; N = 8.5
then it will pay off, but takes a reasonable amount of events (9). The
additional benefit is avoiding memory fragmentation and it would
reduce search for events as you know just events of a given type would
be in the array slot.
For evas_object_smart_callback we could optimize if the smart class
declares its signals and just emits that, in this case we can use a
similar approach to the above.
--
Gustavo Sverzut Barbieri
http://profusion.mobi embedded systems
--------------------------------------
MSN: [email protected]
Skype: gsbarbieri
Mobile: +55 (19) 9225-2202
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