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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