Don't use XML where it doesn't make sense. XML is not a panacea.
You will not get good performance by transferring and parsing a
lot of XML files.
Using XML is memory, CPU, and network intensive.
Avoid creating a new parser each time you parse; reuse parser
instances. A pool of reusable parser instances might be a good idea
if you have multiple threads parsing at the same time.
|Parsing Documents Performance|
- Convert the document to US ASCII ("US-ASCII") or Unicode
("UTF-8" or "UTF-16") before parsing. Documents written using
ASCII are the fastest to parse because each character is
guaranteed to be a single byte and map directly to their
equivalent Unicode value. For documents that contain Unicode
characters beyond the ASCII range, multiple byte sequences
must be read and converted for each character. There is a
performance penalty for this conversion. The UTF-16 encoding
alleviates some of this penalty because each character is
specified using two bytes, assuming no surrogate characters.
However, using UTF-16 can roughly double the size of the
original document which takes longer to parse.
- Explicitly specify "US-ASCII" encoding if your document is in
ASCII format. If no encoding is specified, the XML specification
requires the parser to assume UTF-8 which is slower to process.
- Avoid external entities and external DTDs. The extra file
opens and transcoding setup is expensive.
- Reduce character count; smaller documents are parsed quicker.
Replace elements with attributes where it makes sense. Avoid
gratuitous use of whitespace because the parser must scan past it.
- Avoid using too many default attributes. Defaulting
attribute values slows down processing.
|XML Application Performance|
- Turn validation off if you don't need it. Validation is
expensive. Also, avoid using a DOCTYPE line in your XML document.
The current version of the parser will always read the DTD if the
DOCTYPE line is specified even when not validating.
- For large documents, avoid using DOM which uses a lot of
memory. Instead, use SAX if appropriate. The DOM parser requires
that the entire document be read into memory before the
application processes the document. The SAX parser uses very
little memory and notifies the application as parts of the
document are parsed.