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Re: [vox-tech] Need X Windows performance monitoring help
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Re: [vox-tech] Need X Windows performance monitoring help



On Thursday 15 August 2002 21:19, Peter Jay Salzman wrote:
> eric,
>
> begin Eric Nelson <en77@attbi.com>
>
> > We are developing an embedded system which uses Java and X
> > Windows. It doesn't have a VGA.
>
> embedded and java seems like an oxymoron to me.   :)

I agree, but that's what the guys closest to the purse strings want.
>
> > When we run some code on a desktop with lots of ram and vga, we
> > get pretty good performance, but on our embedded system,
> > performance is poor.
> >
> > There are several factors which may contribute to this problem:
> > swapping of the libraries or X Server itself,latency in the X
> > Server, processor speed, Java, the video driver, etc.  So maybe
> > we need more ram, or a faster video driver, or to lock X into
> > ram, or simply go to a faster clock.
> >
> > My question is, how can we time stamp events,
>
> what do you mean by "time stamp"?  depending on what you mean, i
> would either recommend using the "time" command or the "top"
> command.

What I mean is, 
request to show image -> Xserver 10:43:42.234
Xserver sends commands to hardware 10:43:42.678
image shows 10:43:43.012
etc.  
In the time from start to finish, where are the hangups.  In other 
words, do we need to improve the graphics adapter, the Xserver, add 
ram, what?

We can film the screen, and see how much time things take there, but 
where are other delays? 
>
> > or get a trace of memory
>
> i'm not exactly sure what a memory trace is, either.   but if it
> helps, take a look at /proc/meminfo and see if that shows what you
> want.
>
meminfo and ps have good data, but you would like to see what they 
say, each, say 10 milliseconds.  

Taking the analytical approach, we can put hooks in the code, say 
toggle a bit on the parallel port, and watch w/ a logic analyzer, 
but, whew, what a job.  I was hoping to get some type of strace w/ 
time stamps.

The kind of ironic thing is that, w/ 8 bit processors, a good analyzer 
will do all these things.  Now, with the complexity of modern OS's, 
it's almost like going back to the very early days of microprocessor 
development, as far as tools go.  Like, printk is about the most 
powerful tool out there :~)

> if that's not what you want, take a look at top.
>
> > and swap usage,
>
> ok, that i know.   try:
>
>    cat /proc/swaps
>
> to get how much swap is being used.  if you want to know what
> processes have been swaped to disk, it's good old "ps".  see "man
> ps" and do a search on "swap".

I read somewhere that maybe the libraries swap out.  How can I tell?
>
> i saw rod's reply.  as usual, he makes total sense.  :)

Yes, often the empirical approach is easiest, and since you are 
measuring what you want to measure, and not some artificial 
byproduct, it's more accurate.  And, you get the quickest results.  
We vary ram, clock speed, maybe even different graphics adapters.  
I'm pretty sure that's the best, most direct approach.

Thanks.

>
> pete

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