Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!think!mintaka!bloom-beacon!EXPO.LCS.MIT.EDU!keith
From: keith@EXPO.LCS.MIT.EDU (Keith Packard)
Newsgroups: comp.windows.x
Subject: Re: Confusing performance data about XNEWS and R4
Message-ID: <9002231642.AA11943@xenon.lcs.mit.edu>
Date: 23 Feb 90 16:42:31 GMT
References: <22345@pasteur.Berkeley.EDU>
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 35


> I found some confusing performance data about
> the R4 server and OpenWindows 1.0 (XNEWS) on my SPARC-1 (No GX board).
> 
> For my own program that draws a lot vectors with "XDrawLines",
> OpenWindows is about 3 times faster than the R4 server
> to draw the complete picture on the screen.
> (measured with a stop watch, not CPU time)
> 
> However, for "x11perf -line???" (??? is any legal number),
> the results show that R4 server is about 50% faster than the OpenWindows.
> 
> Does anyone know why?

The R4 server was tuned to draw only copy-mode lines with a planemask of
all ones.  If your application uses some other raster op, or other planemask,
the performance of the R4 server will be abysmal.  Time constraints prevented
me from spending the week necessary to rewrite the line code for faster
non-copy mode lines.

Also, x11perf attempts to represent the "perfect" client.  The performance data
it generates are best case numbers.  In the case of XDrawLines, x11perf draws
hundreds of lines in each request.  The R4 server was extensively tuned to run
x11perf quickly which could possibly have impacted the performance for clients
which draw few objects at a time (I don't think this is the case, but I have
no performance data to support this position).

So, if you application drew more lines at a time you could expect the
performance of the R4 server to improve.

Given the wide disparity between the XNEWS server and the R4 server for your
application, I suspect the first cause is more likely than the second.

Keith Packard
MIT X Consortium