[Mono-dev] [PATCH] - optimization for System.Xml.XmlNode::SelectSingleNode

[Atsushi Eno]

Well, it wasn't really internal, but that does not affect my statement.

Atsushi Eno

On 2010/05/11 2:55, Atsushi Eno wrote:
> Hi,
>
> Thanks Tom, it looks like a good catch. The interface is internal, and
> cast exceptions should not happen there anyways. Once the build got
> fixed, I'll verify the patch and apply it unless it regresses.
>
> Atsushi Eno
>
>
> On 2010/05/11 2:09, tom hindle wrote:
>    
>> Hi,
>>
>> While performance profiling our code, with mono's nice profiling
>> tools :), I noticed System.Xml.XmlNode::SelectSingleNode was taking 23ms
>> a call while the sum of the methods it was calling took<   5ms.
>> SelectSingleNode is a very simple method however it contains a (dynamic)
>> down cast. I replaced the (Cstyle/prefix) cast with a 'as' cast and this
>> seem to reduce the method time by about 7ms.
>>
>>
>> // With 'Cstyle' cast
>>    39672.303    1717   23.106
>> System.Xml.XmlNode::SelectSingleNode(string,XmlNamespaceManager)
>>     Callers (with count) that contribute at least for 1%:
>>           1717  100 % System.Xml.XmlNode::SelectSingleNode(string)
>>
>> // With 'as' cast
>>    29238.117    1880   15.552
>> System.Xml.XmlNode::SelectSingleNode(string,XmlNamespaceManager)
>>     Callers (with count) that contribute at least for 1%:
>>           1880  100 % System.Xml.XmlNode::SelectSingleNode(string)
>>
>>
>> I read that this is because 'as' cast generates IL instr 'isinst' while
>> 'cstyle' cast generates 'castclass'.
>>
>> The msdn documentation about XmlNode.SelectSingleNode doesn't state that
>> an InvalidCastException, can/could be thrown.
>>
>> Is this a sensible thing to do? If so could someone review/commit my
>> patch as I believe it will make a fairly major difference for
>> applications that make much use of SelectSingleNode.
>>
>>
>> Thanks
>> Tom
>>
>>
>>
>> _______________________________________________
>> Mono-devel-list mailing list
>> Mono-devel-list at lists.ximian.com
>> http://lists.ximian.com/mailman/listinfo/mono-devel-list
>>
>>      
> _______________________________________________
> Mono-devel-list mailing list
> Mono-devel-list at lists.ximian.com
> http://lists.ximian.com/mailman/listinfo/mono-devel-list
>
>
>
>