#2030 NORM Trial-3: Activity wedge memory footprint representation

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#2030: Activity wedge memory footprint representation
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  Reporter:  Eben    |       Owner:  marco   
      Type:  defect  |      Status:  reopened
  Priority:  normal  |   Milestone:  Trial-3 
 Component:  sugar   |     Version:          
Resolution:          |    Keywords:          
  Verified:  0       |  
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Comment (by danw):

 Replying to [comment:21 Eben]:
 > I've just tried this out in the latest build, and it doesn't appear to
 be representing things accurately.  It appears as though it's using some
 kind of relative scale, because the size of each wedge decreases by a
 significant amount every time a new activity is opened.

 Hm... OK, it's not *intentionally* relative, but yeah. The problem is:

  1. The ring doesn't represent "all RAM", it represents "all RAM that is
 either free, or used by an activity". (ie, RAM used by non-Activity
 processes doesn't show up *anywhere*, so we can't just say that the ring
 represents 256M of RAM).
  2. We're consistently overestimating the amount of RAM used by
 activities.

 Since we don't know a priori how much RAM the whole ring represents, we
 have to calculate it as being the sum of all RAM used by activities, plus
 the amount of free RAM. But since we're overestimating the RAM used by
 activities, that means each time you start a new activity, the estimate of
 total RAM ends up increasing, meaning the percentage of the ring used by
 each activity decreases.

 I think we can fix the overestimate by reading the detailed memory map
 (/proc/PID/smaps) for each process, and adding up only the private
 mappings, plus a percentage of any shared mappings (depending on how many
 activities they were shared between). And anything that was mapped by the
 sugar shell wouldn't count at all against any activity, because it would
 be in use whether or not the activities were using it.

-- 
Ticket URL: <http://dev.laptop.org/ticket/2030#comment:22>
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