Re: [dotNetRDF-Develop] WP7 Memory Usage

[Rob V. <rv...@do...>]

Hi Steve
I am not a Windows Phone expert so it is hard to tell what might be 
happening.
Firstly how are you measuring the memory used?  If you are using 
GC.GetTotalMemory() then the GC has the option of invoking a garbage 
collection when you call that method, if you've set the boolean parameter 
to true it will wait for that collection before reporting memory used which 
will eliminate any temporary objects that have yet to be collected.  In 
general I would expect the Windows Phone GC to be fairly proactive at 
freeing up memory as obviously a phone has limited RAM.
If you aren't already you should try using the Windows Phone 7 memory usage 
metrics, see 
http://blogs.msdn.com/b/mikeormond/archive/2010/12/16/monitoring-memory-usag
e-on-windows-phone-7.aspx for a nice blog post on this.
In terms of memory usage for the result set this may be very small 
depending on the size of your results and the values involved.  Typically a 
triple takes around 1 KB (assuming you don't have really long literals) so 
an individual node takes about 300 bytes or so.  So say you had 10 results 
with 3 values for each result you'd only use about 10 KB of memory 
(possibly less depending on the exact values). If your results set has 
fewer columns or all the values are very short then this memory usage may 
be far less.
A SparqlResultSet has minimal memory overhead since internally it is a 
couple of lists and similarly an individual SparqlResult is internally a 
small dictionary.
In contrast IGraph implementations typically exhibit much higher memory 
overhead because they incorporate indexes on the triples.  For example the 
default Graph implementation which is fully indexed takes ~1.7 KB per 
triple on average as opposed to a non-indexed implementation like 
NonIndexedGraph which requires only ~1 KB per triple (i.e. there is an 
extra 0.7 KB per triple for indexing)
Also your memory usage may be affected by temporary objects, so if you 
created a SparqlRemoteEndpoint instance local to a method in order to make 
the query and check the initial memory usage in that method then that 
object would be out of scope and potentially GCd by the time you check the 
final memory usage.
Hope that helps,
Rob

----------------------------------------
From: "Steve S" <s....@li...>
Sent: 05 September 2011 18:56
To: "Rob Vesse" <rv...@do...>
Subject: RE: [dotNetRDF-Develop] WP7 Memory Usage 




Hi Rob,

I am trying to get the memory usage of Windows Phone 7 when getting a 
response from sparql endpoint via HTTP using dotNetRdf for Windows Phone 7. 
I am calculating the memory used before the request is sent and then just 
after receiving the reply (in the ResultsCallBack method). I was expecting 
the second memory calculation to be higher than the first, but instead it 
is either the same or lower than the first reading. Is that normal for WP7 
or is this because of the asynchronous callback or am I doing something 
wrong?

Regards,
Steve