Re: Re: about your concept

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Friday 23 July 2004 22.47 skrev Andrew Suffield:
> > We can also assume that the
> > message-retrieval from socket should be as one big chunk + one small
> > chunk first to know the length.
> No, that's (a) a performance disaster, (b) not possible on unix, and
> (c) not how the code works.
(a) Are you saying exceuting unnecessary syscalls (such as read) is not 
performance impact
(b) Why not possible on unix?
(c) No, I see you've got a better solution, buffering data to read the entire 
message from socket in 1 big chunk (unless the message is fragmented on 
socket-level with big timeout, which could not have been avoided anyways). 

> > The only case I can see, where breaking alignment is
> > possible, is if there is a string parameter that is not exactly 4 bytes
> > in length.
> ...or when you are on a system with 8-byte alignment. The whole thing
> is stupid and pointless, it's an exercise in targetting one specific
> piece of hardware at the expense of all others.
That part is true. I don't know if there today is any 8-byte aligned 
architectures, but as Brandon pointed out, there might be, or might be in the 
future.

> > So if we added an explicit rule, that each parameter should always
> > start at 4 bytes aligned offset from message start, the entire problem
> > would be solved, allowing better performance on RISC architectures.
> Only it would really just slow them down a little some of the time,
> and otherwise have no effect. You don't have any clue how the code
> works, do you?
Actually, on a pentium-class x86 or above, or on any other pipelined 
architecture, I don't think there would be any performance-hit at all, and if 
we did agree on the 4-byte alignment on some RISC, and it's performance 
impact of addressing int:s, there would be a few systems that would benefit 
from it. However, as pointed out above, 4-byte alignment isn't certain to be 
the only preferred alignment in the vast amount of architectures that Y has 
to support.

> > To implement
> > this in the server and client is really simple
> s/simple/hard/, you'd have to completely rewrite the socket code and
> break it in the process.
Are you so afraid of touching your own code? Actually the only thing you'd 
have to touch is messageFromString and it's equivalent in the client-libs. 

However, due to Brandons comment about adjusting the protocol to one type of 
alignment, where there might be other preferred alignments today or in the 
future, I'd say it's a waste of time. You go ahead with your business.

Regards
/ Ulrik

- -- 
When you are about to die, a wombat is better than no company at all.
		-- Roger Zelazny, "Doorways in the Sand"
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