On Aug 13, 2012, at 8:49 PM, soyo <[email protected]> wrote:
> As for checking the RAM usage, the task manager.
Interesting. I hadn't seen those process sizes before...
So, as a "walkthrough", let's consider the Hello World sample:
https://github.com/xamarin/monodroid-samples/tree/master/HelloWorld
I've got it running on an x86 emulator and a Galaxy Nexus; alas, not all of
what follows applies to both...
So, as per Settings > Apps > Running > Show Cached Processes >
mono.samples.helloworld, the Galaxy Nexus states that the process is 8.7MB in
size, while the x86 emu says it's 8.8MB.
PS output: x86:
$ adb -e shell ps | grep hellowo
app_55 1451 779 207184 31596 ffffffff b7ed8ed7 S
mono.samples.helloworld
PS output: ARM:
$ adb -d shell ps | grep hellowo
u0_a99 28904 124 486732 34176 ffffffff 00000000 S
mono.samples.helloworld
What are we looking for?
$ adb -e shell ps -p 1451
USER PID PPID VSIZE RSS PRIO NICE RTPRI SCHED WCHAN PC NAME
app_55 1451 779 207184 31596 20 0 0 3 ffffffff b7ed8ed7 S
mono.samples.helloworld
The 4th column is VSIZE, while the 5th column is RSS (Resident Set Size);
sizes are in KB. Thus, on each platform there's ~31-34MB in RSS, which (1)
sounds huge, and (2) is quite different from what the Settings app is reporting.
Want more detailed memory use? Check /proc/PID/status:
x86 (abbreviated):
$ adb -e shell cat /proc/1451/status
Name: ples.helloworld
State: S (sleeping)
VmPeak: 208684 kB
VmSize: 207184 kB
VmLck: 0 kB
VmHWM: 33068 kB
VmRSS: 31596 kB
VmData: 32192 kB
VmStk: 84 kB
VmExe: 8 kB
VmLib: 51088 kB
VmPTE: 160 kB
ARM:
$ adb -d shell cat /proc/28904/status
Name: ples.helloworld
State: S (sleeping)
VmPeak: 491164 kB
VmSize: 486732 kB
VmLck: 0 kB
VmHWM: 37572 kB
VmRSS: 34176 kB
VmData: 28340 kB
VmStk: 136 kB
VmExe: 8 kB
VmLib: 29736 kB
VmPTE: 130 kB
VmSwap: 0 kB
Certainly more human readable than `ps` output, but I still have no idea where
the 8MB is coming from. Bizarre...
Regardless, those numbers are still _huge_. Where's all the memory _going_?
This is where the unlocked hardware falls down: /proc/PID/smaps has the desired
information, but it's not accessible on unrooted devices:
$ adb -e shell cat /proc/1451/smaps
08048000-0804a000 r-xp 00000000 1f:00 464 /system/bin/app_process
Size: 8 kB
Rss: 4 kB
Pss: 0 kB
Shared_Clean: 4 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 4 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
...
0877d000-08ab1000 rw-p 0877d000 00:00 0 [heap]
Size: 3280 kB
Rss: 3280 kB
Pss: 2331 kB
Shared_Clean: 0 kB
Shared_Dirty: 1000 kB
Private_Clean: 0 kB
Private_Dirty: 2280 kB
Referenced: 2392 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
...
It's...huge. You'll certainly want to redirect that to a file. ;-)
What you'll find is that _most_ of the memory is being used by "data" -- shared
libraries, fonts, etc. What's interesting is the "Private_Dirty" and
"Shared_Dirty" values; let's sum them up:
# sanity check; note that the value is fairly close to the previous
VmPeak size in the /proc/PID/status output
$ adb -e shell cat /proc/1451/smaps | grep Size | awk '{ sum += $2 }
END {print sum " kB"}'
209112 kB
$ adb -e shell cat /proc/1451/smaps | grep Private_Dirty | awk '{ sum
+= $2 } END {print sum " kB"}'
4212 kB
$ adb -e shell cat /proc/1451/smaps | grep Shared_Dirty | awk '{ sum +=
$2 } END {print sum " kB"}'
15036 kB
# sanity; note that Private_Dirty+Shared_Dirty = Dirty
$ adb -e shell cat /proc/1451/smaps | grep Dirty | awk '{ sum += $2 }
END {print sum " kB"}'
19248 kB
So ~4MB is private/unshared, and ~15MB is private/shared. There's nothing that
can be done about the Shared_Dirty mappings (it's due to ld.so/etc.), so out of
the original ~32MB RSS value, only 4MB was actually written to between Android
& Mono for Android (for this process).
I'm still not sure where the Settings app is getting 8MB from, but it appears
to have no relation to any of the above information...
- Jon
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