Re: [xml] per thread memory

[Daniel Veillard <veillard redhat com>]

On Sat, Jul 19, 2003 at 06:40:46PM +0100, Graham Bennett wrote:
> Another question,
>
> Is there any information about the --with-thread-alloc option and how it
> is implemented?  I just noticed it when configuring 2.5.8.

  It's probably not what you have in mind. Basically xmlMalloc()/xmlFree()
and xmlRealloc() are global variables, by default they are shared between
threads, if this option is passed each thread has its own copy.

> I have some multithreaded test cases, so I'm intending to enable this
> option and see what kind of improvement I get.

  That won't improve anything. Only if you define your own memory allocation
pool (for example for workers within an apache process) then this may be
a improvement to have separate, per thread routine.

> Are there any known problems (performance or otherwise) with thread
> safety and the --with-threads option?  From what I can see all my code
> will need to do is to call xmlInitParser() under a mutex.  Does it
> matter if the function is called more than once (not concurrently)?

  This should work fine, the only problem I'm aware of is a thread
problem when using NTPL on Linux on PowerPC 64 bits. Seems that
xmlInitParser() should be callable twice, yes... if not it's a bug.

Daniel

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