[Dovecot] Dovecot - some more optimisations

[Len7hir]

I did some more optimisation.


Most performance hit in Dovecot do "for loop" in string operations.

In one case (in message-parser.c) "for loop" has another "for" inside 
with the same variable used as iterator. This case is very hard to 
optimise by compiler.

I do changes only in top functions listed in oprofile.
Maybe I do more in future.


Code was analysed and tested but it's hard to generate all cases.
It's working well in production server (I'm monitoring).


In istream-crlf.c I've changed one thing.
When destination buffer is full after '\r' addition (to dest), It didn't 
skip '\n' in source buffer. I think this was buggy in earlier code, and 
'\n' was skipped (this piece of code is used very rare).


Please check this out. This can help in huge e-mail systems :P


And another problem. Why You use safe_memset instead of memset?
Now this function have the largest impact in Dovecot performance.
Another on list is t_push.


Regards,
Len7hir
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