[Interest] Question to members of the Qt team: why does an empty project consumes so much memory on iOS?
Nuno Santos
nunosantos at imaginando.pt
Tue Apr 21 19:43:31 CEST 2015
Thiago,
Thanks for your explanation.
Right now I don’t have a clue on how should I correctly measure occupied by one Qt app on iOS environment.
I need to dig it out.
Thanks,
Regards,
Nuno
> On 21 Apr 2015, at 18:30, Thiago Macieira <thiago.macieira at intel.com> wrote:
>
> On Tuesday 21 April 2015 18:16:57 Nuno Santos wrote:
>> Thiago,
>>
>> Sorry for not having replied to you. I missed your email.
>>
>> "Is that 16 MB of heap? Or are you including sharable & discardable code
>> pages?”
>>
>> Sorry but I really don’t know what to answer here.
>>
>> I’m just launching a new and empty Qt Quick project on Xcode and looking to
>> the memory usage.
>
> The point is that you're not measuring memory properly.
>
> Let me take the example of Qt Creator
>
> F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND
> 0 1000 51459 2285 20 0 3085928 127168 - Sl+ pts/0 9:12
> bin/qtcreator
>
> How much memory is it consuming? Would you answer 2.94 GB? Maybe 124 MB?
>
> The answer is yes and no for both numbers. It depends on what you're
> measuring. And there are more numbers:
>
> $ ~/src/owntools/rssanalyse/rssanalyse.pl `pidof qtcreator`
> Total mapped memory: 3085932 kB
> of which is padding: 1933552 kB
> of which swapped out: 669832 kB
> of which likely stack: 32908 kB mapped, 108 kB resident (64 kB main, 44 kB
> aux threads)
> of which are resident: 130152 kB, 123534 kB proportionally shared
> total anonymous: 98168 kB (75.4%)
> Shared: 10200 kB total (7.8% of RSS)
> Breakdown: 3476 kB clean (34.1%), 6724 kB dirty (65.9%)
> 3100 kB code (30.4%), 376 kB RO data (3.7%), 6724 kB
> RW data (65.9%)
> 0 kB heap (0.0%), 0 kB stack (0.0%), 0 kB other
> (0.0%)
> Private: 119952 kB total (92.2% of RSS)
> Breakdown: 32600 kB clean (27.2%), 87352 kB dirty (72.8%)
> 21768 kB code (18.1%), 1052 kB RO data (0.9%), 360 kB
> RW data (0.3%)
> 96652 kB heap (80.6%), 108 kB stack (0.1%), 12 kB
> other (0.0%)
>
> The number in VSZ is usually not quoted because, as you can see, 62% of it is
> *padding* between sections of RAM.
>
> 124 MB is how much it really uses in RAM, but 10 of those is clean & shared
> and another 32 MB is clean & sharable (but not shared, because no other
> process loads the Qt Creator libraries). All clean pages can be discarded on
> memory pressure and reloaded from disk.
>
> Then there's 654 MB that is swapped out.
> --
> Thiago Macieira - thiago.macieira (AT) intel.com
> Software Architect - Intel Open Source Technology Center
>
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