Save
save
Saving a document is generally sloowing Table Summarizes The Differences:
Save a document is always more than loaded. The following table shows the difference:
Sample sample
Load (millisecond) loading (millisecond)
Save (MilliseConds) Save (milliseconds)
Difference (percentage) difference (percentage)
ADO.XML
677
1,441
113
Hamlet.xml
104
184
77
Ot.xml
1,063
1,971
85
Northwind.xml
62
103
66
When saving each sample, the worst case is the attribute-heavy ADO Recordset, which is more than twice as slow as loading it into memory. Given that it seems perfectly reasonable to expect a write operation to be slower than a read operation, these numbers Are Rather Good. But Be Careful. You Can Easily Strain The File System if You Are Loading and Saving Lots of Small XML Documents, AS Shown In The section "Free-Threaded Documents".
When each sample file is saved, the worst case occurs on the Ado Recordset file with a large bit, and its write time is twice as slower than loaded. Since the write operation is generally considered to be more reasonable than reading operation, everyone can accept it. But please note that if you load and save a lot of small XML documents, the file system is likely to be affected, just as the "Free Thread Document" will be discussed.
Namespaces
Name space
XML Namespaces also add some overhead in XML parsing time, but not as much as you might think I have two versions of the Ado.xml example One uses a namespace prefix "recordset:".. On all 2,347 rows, and one does not. The Following Table Shows The Difference In Load Time:
XML namespace has also added some XML analysis, but it is not as much as you think. Here are two versions of ADO.xml examples. One of them uses "Recordset:" prefix in 2,347, and the other is not. The table below shows their difference in load time:
Measurement metrics
ADO.XML
ADO-NS.XML
Difference (percentage) difference (percentage)
FILE SIZE file size
1,007,214
1,030,651
2.3
Load Time (MilliseConds) load time (ms)
662
680
2.7
Most of the difference in loading time can be explained by the increable in file size.
Free-threaded Documents free thread document
A "free-threaded" DOM document (CLSID_DOMFreeThreadedDocument, "Microsoft.FreeThreadedXMLDOM") exposes the same interface as the "rental" threaded document (IID_IXMLDOMDocument). This object can be safely shared across any thread in the same process.
Free Thread DOM Document (CLSID_DOMFREETHREETEDDocument, "Microsoft.FreethreadEDXMLDOM") provides the same interface as the leased thread document (IID_ixmldomDocument). This object can be safely shared at any of the same process in the same process.
Free-threaded documents are generally slower than rental documents because of the extra thread safety work they do. You use them when you want to share a document among multiple threads at the same time, avoiding the need for each of those threads to load up their OWN Copy. in Scenarios, this Can Result in A Big Win That Outweight Safety Work.
The free thread document is generally slower than the rental thread document because it is expelled for thread security. If you want to share a document in multiple threads, you can use it to avoid loading your own copy at each thread. In some cases, this will greatly improve performance, even in additional overhead even on thread security.
For Example, Suppose You Have A 2-KB XML FILE ON YOUR Web Server, And You Have A Simple ASP Page That Loads That File, Inside The File, And Saves The File Again.
For example, assume that there is a 2KB XML file on your web server, and a simple ASP page To load this file, add an attribute in the file and save it.
<% @ Language = jscript%>
<%
Response.expires = -1;
Var filename = server.mappath ("simple.xml");
Application.lock ();
Var Doc = Server.createObject ("Microsoft.xmLDom");
Doc.async = false;
Doc.Load (filename);
VAR C = PARSEINT (Doc.Documentelement.getattribute ("count")) 1;
Doc.documentelement.setttribute ("count", c);
Doc.save (filename);
Application.unlock ();
%>
<% = C%>
This ASP Code Will Be Completely Disk I / O Bound. On My Pentium II 450-MHz Dual-Processor Computer, I Was Not Able To Get Any More Than 50 Percent CPU Utilization. The Disk Was Making A Lot of Noise.
This ASP code will greatly occupy disk read and write channels. On my Pentium II 450-MHz dual processor, I can't get more than 50% of the CPU usage.
However, We Could Bring The File Into Shared-Application State Using A Free-Threaded Dom Document, As Follows:
However, we can use the free thread DOM document to share the file, the code is as follows:
<% @ Language = jscript%>
<%
Response.expires = -1;
VAR DOC = Application ("Shared");
IF (DOC == Null)
{
DOC = Server.createObject ("Microsoft.FreethreadedEdXMLDOM");
Doc.async = false;
Doc.Load (Server.MAppath ("Simple.xml");
Application ("Shared") = DOC;
}
Application.lock ();
VAR C = PARSEINT (Doc.Documentelement.getattribute ("count")) 1;
Doc.documentelement.setttribute ("count", c);
Application.unlock ();
%>
<% = C%>
THEN WE WOULD See The Throughput Jump DramAtical
In this way, we can see the dramatic leap in throughput:
Method method
REQUESTS / Second request / second
LOAD / SAVE load / save
34
Shared sharing
250
In Other Words, this Second Approach Using The Free-Threaded Dom Document Is Seven Times Faster Than The Other!
It can be said that the second method of using the free thread DOM document is 7 times faster than the first method.
Delayed Memory Cleanup
Delayed memory release
The one downside to the free-threaded model is that it exhibits more latency in how it cleans up unused memory, affecting the performance of subsequent operations. (Some people report this as a memory leak when in fact it is just delayed cleanup.) The . larger the XML document, the more pronounced the latency the following table shows the increase in load time and working set when using the free-threaded document as opposed to the rental document: a free-threaded model is the lack of it in the release of unused There is a delay in memory space, which affects the performance of follow-up. (Some people report this phenomenon as memory leaks, in fact, it is just lazy release of memory.) The larger the XML document, the more delayed. The following table shows the use of free threads with the use of leased mode in load time and workspace:
Sample sample
Load Time (Percentage Increase) load time (incremental percentage)
Working set (percentage increase) Workspace (incremental percentage)
ADO.XML
4
137
Hamlet.xml
twenty three
83
Ot.xml
1
53
Northwind.xml
2
42
These results show that the worst case is when you have many nodes (as in Ado.xml), which makes sense because this generates more memory for the memory manager to clean up. Note that the benefits of being able to share the same document object Across Threads, AS Shown Above, Still Outweigh The Downside of Slower Load Time And a Larger Working Set.
The above results indicate that the worst case occurs on documents with many nodes (just like in ADO.xml). Please note that the benefits of sharing documents between threads, as shown above, still exceeding its adverse effects on load time and working space.
Virtual memory
Virtual Memory
In the free-threaded model, the working set can spike if you generate enormous amounts of memory for the memory manager to clean up-which can happen when performing XSL transformations on large documents. In this case, you will use up all available memory and strain the virtual memory manager, causing the performance to dramatically decrease. Watch the peak working set of your application under a heavy load to make sure this does not happen. If it does, redesign your application by breaking the XML down into smaller chunks. This Situation Has Been Improved Somewhat In The Msxml January 2000 Web Release. In Fact, We Got The Following Reader Comment On The January 2000 Web Release Page: In the free thread mode, the workspace will increase, if you have a lot of memory needs Manage the release of the memory, which occurs when the XSL conversion of the big document. In this case, you will use the available memory resources, and frequently call the virtual memory manager, and the performance has dropped sharply. You can determine this phenomenon without happening by observing the peak workspace of the application in high load. If you have happen, you can open XML into small pieces, redesign your application. This situation has improved in MSXML January 2000 Web Release. In fact, we get the following readers commented:
FASTER!
Faster!
I'VE DONE A Couple of Informal Speed Trials On Server-Side Transforms (XML TO HTML VIA XSL), and NOTMED That There's A Big Improvement.
I did some informal server-side conversion (converted to HTML via XSL to HTML) speed testing, and found a huge improvement.
- Anonymous 9-Feb-2000
- Anonymous 2-9,2000
Idispatch
Idispatch
Late-bound scripting languages, such as JScript and VBScript, add a lot of overhead to each method call and property access in the DOM interface. The script engines actually invoke the methods and properties indirectly through the IDispatch interface. First, both script engines call GetIDsOfNames or GetDispID, which will pass in a string name for the method or property and return a DISPID. Then the engines package all the arguments into an array and call Invoke with the DISPID. late binding (late-bound) scripting language, such as JSCIRPT and VBSCIRPT add a lot of overhead when modified and attribute accesses each time the DOM interface. The script engine is actually the indirect calls and properties through the IDispatch interface. First, the scripting engine calls GetIDSOFNAMES or GETDISPID, incoming methods, and attribute name strings, returns a DISPID. Then the engine packs all the parameters to an array and calls Invoke with Dispid.
Need I say more Clearly, this is going to be slower than calling a virtual function in C or compiled Visual Basic Visual Basic is a bit tricky, though, because you can actually do both styles of programming in one application For example?..:
Neat more information? Obviously, this is slower than calling a C virtual function or compiled Visual Basic. But Visual Basic is complex because you can use two programming methods in an application. E.g:
DIM DOC AS Object
SET DOC = CreateObject ("Microsoft.xmldom")
...
This is late-bound and will be as slow as VBScript or JScript. To speed this up, from the Project menu, select References and add a reference to the latest version of the "Microsoft XML" library. Then you can write the following early -Bound Code:
This is late binding, will be as slow as VBScript and JScript. In order to improve the speed, press the Project menu, select References and join the latest version of the Microsoft XML library. Then you can write the following early binding code:
Dim Doc as new msxml.domdocument
...
Another advantage of this programming method is another advantage of this programming method in Visual Basic in Visual Basic in Visual Basic. Get various method names and other help information.
