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xen-devel
Re: [Xen-devel] [PATCH 3/4] libxl: add version_info function [and 1 more
On 19/04/10 21:43, Andre Przywara wrote:
I am not fully convinced of this. There is quite a lot of information
copied (up to 4KB), and some fields (like pagesize or the version
numbers) are just plain integers. And this approach just propagates the
underlying design.
In the xl info implementation I used this feature to just get the
pagesize. One could think of just querying the version number, too. If
you don't like the additional parameter, what about a wrapping macro, then?
I don't see the problem with the complexity, though, as it is hidden
inside the library.
The query mask is exposed to the user, and the structure is partially
filled. I can imagine that it's going to create those kind of issues,
where the wrong mask is passed, or change later, and then the field the
user was expecting would be left null.
The macro would help in the previous case, but I still feel it's
unnecessary. As a user, I would just not bother, and call the function
always with full mask, until I reach the optimisation phase, and its
appears on the graph.
A couple of K of data copied shouldn't make a difference, and would be
completely lost in noise, however if you really think it makes a
difference, you could have special dedicated info call to get specific
things like version number.
I can use libxl_sprintf function to get rid of the free() function, but
I personally don't like the idea of accumulated mallocs much, left alone
the "hidden" free operation.
There is a real advantage of permitting a fast development of libxl (and
its bindings).
This was to get started at the beggining; when we reach a point where
everything is working we could improve or remove the memory system. But
I'm fairly convinced it's not going to make a difference for this kind
of library.
--
Vincent
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