'Write attribute vs Write procedure.

[Jano <nono@celes.unizar.es>]

Hi everybody.

I'm getting abysmal differences in speed when writing large chunks (64k) 
of data to a stream. The stream is from a socket of Gnat.Sockets, I 
mention it because I don't know if it has something to do.

See the two following snippets of code:

----common-----
Buffer : Stream_element_array (1 .. 
            Stream_element_offset (Upload_buffer_size));
----common-----

----case A-----
Write (This.Link.all, 
   Buffer (1 .. Stream_element_offset (Chunk)));
----case A-----

----case B-----
Stream_element_array'Write (This.Link, 
   Buffer (1 .. Stream_element_offset (Chunk)));
----case B-----

In the above example (without optimizations and -O2 tried, both the 
same), the Write procedure is taking no noticeable amount of time/cpu. 
In the contrary, the 'Write attribute takes like 3-4 seconds of 100% CPU 
usage, shared more or less equally by my program and the SYSTEM process, 
whatever it is, on WinXP. Compiler is Gnat 3.15p, computer Pentium III 
450Mhz.

I'm asking only out of curiosity, and to prevent any other surprise in 
the future. Could it be related to alignment checks/adjustments?

P.s: The 'Read attribute is also fast, no noticeable delay.

P.s2: I've tried also with strings, only the 'Write version of course, 
and results are the same.

-- 
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Jano
402450.at.cepsz.unizar.es
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