[Xastir-dev] Xastir a CPU pig again?

[Tom Russo]

On Thu, Dec 25, 2003 at 05:16:51PM -0700, a Mr. Richard Feyler of Fort Lee, New Jersey <russo at bogoflux.losalamos.nm.us> writes 'Dear Rosanne Rosannadanna':
> On Thu, Dec 25, 2003 at 06:08:33PM -0500, a Mr. Richard Feyler of Fort Lee, New Jersey <bdheaton at c4i2.com> writes 'Dear Rosanne Rosannadanna':
> > On Thu, 2003-12-25 at 18:05, Tom Russo wrote:
> > > I can confirm it is in fact exactly the source of the problem.  I
> > > changed the 100us delay in interface.c that had been reduced from
> > > 200ms sometime between 4 Dec and 8 Dec.  In the 25 Dec CVS version
> > > this is on line 5307.  Setting it to 100ms instead of 100us ended my
> > > problems.  With that change (and no other) both the 8 Dec and current
> > > CVS versions of Xastir are back down to taking negligible CPU times.
> 
> > > Now to figure out if the issue with CVS gdal instead of gdal-1.1.9
> > > is a real one, or just a red herring.
> 
> > 
> > 	Interesting.  I wonder if th 100us vs. 100ms was a typo when the change
> > was committed? 
> 
> Well, the tmv.tv_usec setting went from 200000 to 100 in one edit, and
> the units in the comments changed to match it as well.  I'm guessin'
> it was intentional and related to the change that resulted in the
> inter-char pacing slider.

Actually, the commit log shows that it was indeed intentional:

-------------------------
Revision 1.146
Sun Dec 7 20:23:28 2003 UTC (2 weeks, 4 days ago) by we7u
Changes since 1.145: +4 -3 lines

Reducing delay in port_write for checking queue.  Down to 100us from 200ms.
Makes writing to interfaces much snappier, but doesn't bog down CPU.
Cranking up channel_data() busy wait from 1 to 2us.

-----------------------

I just finished a quick study in reducing the 100ms delay down to 10ms
and then 1ms.  No CPU bogging here.  Drop it down one more decade to 100us 
and kaboom. 

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://www.qsl.net/~km5vy/
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