On terça-feira, 3 de setembro de 2013 16:16:25, Alex Malyushytskyy wrote: > Even if simply counting % of software which have to handle data exceeding > 32 bit limit on the home personal computer you will get higher %. > Rising of interest in distributed computing including visualization > probably does not meant to solve problems with low memory requirements.
Even today, software that has a core memory of more than 4 GB (or even 2 GB) is an exception, rather than the rule. Please be careful when looking at the memory sizes of some process tools, since they do not represent actual memory usage. In any case, we're talking here about having one single container addressing more than 2 GB of memory. Because of the implicitly shared & copy-on-write nature of the Qt containers, that will probably be highly inefficient. You need to be very careful when writing such code to avoid triggering COW and thus doubling or worse your memory usage. Also, the Qt containers do not handle OOM situations, so if you're anywhere close to your memory limit, Qt containers are the wrong tool to use. The largest process I have on my system is qtcreator and it's also the only one that crosses the 4 GB mark in VSZ (4791 MB). You could argue that it is an indication that 64-bit containers are required, but you'd be wrong: * Qt Creator does not have any container requiring 64-bit sizes, it simply needs 64-bit pointers * It is not using 4 GB of memory. That's just VSZ (mapped memory). The total RAM currently accessible to Creator is merely 348.7 MB. * And it is using more than 4 GB of virtual space *because* it is a 64-bit application. The cause-and-effect relationship is the opposite of what you'd expect. As a proof of this, I checked how much virtual space is consumed by padding: 800 MB. A 32-bit application would never do that, that's 19.5% of the addressable space on 4 GB. (padding is virtual space allocated but not backed by anything; it's only there so that something else doesn't get mapped to those pages) -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center
signature.asc
Description: This is a digitally signed message part.
_______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
