[ace-users] ACE Reactor Timer Dispatching

Douglas C. Schmidt schmidt at dre.vanderbilt.edu
Fri Aug 24 07:44:21 CDT 2007

Hi Prashanth,

To ensure that we have proper version/platform/compiler information,
please make sure you fill out the appropriate problem report form
(PRF), which is in


or in


in older versions of ACE+TAO.  Make sure to include this information
when asking any questions about ACE+TAO since otherwise we have to
"guess" what version/platform/compiler/options you've using, which is
very error-prone and slows down our responsiveness.  If you don't use
the PRF, therefore, it is less likely that someone from the core
ACE+TAO developer team will be able to answer your question.
Naturally, we encourage and appreciate other members of the ACE+TAO
user community who can respond to questions that they have the answers

>I see that the timer skew is set to 10ms in the config-<platform>.h
>files. As a result of this the timers expire earlier (by 10ms).=20
>1) Could someone please clarify on the reason behind this 10ms value?=20

Please see ACE_ROOT/ACE/ace/README

for an overview of ACE_TIMER_SKEW

ACE_TIMER_SKEW                          If a timed ::select () can return
                                        early, then ACE_TIMER_SKEW is the
                                        maximum adjustment, in microseconds,
                                        that ACE_Timer_Queue uses to
                                        compensate for the early return.

>2) Also if this is set to 0 what are the implications?=20
>Something like:
>ACE_TP_Reactor  reactor;
>ACE_Time_Value skew(0,0);
>File: ace/config-sunos5.5.h
>// Maximum compensation (10 ms) for early return from timed ::select ().
>#if !defined (ACE_TIMER_SKEW)
># define ACE_TIMER_SKEW 10 * 1000
>#endif /* ACE_TIMER_SKEW */

It looks like you're using an old version of ACE.  Please upgrade to
ACE+TAO+CIAO x.5.10 (i.e., ACE 5.5.10, TAO 1.5.10, and CIAO 0.5.10),
which you can download from


under the heading: "Latest Beta Kit".  ACE_TIMER_SKEW is no longer set
in the various config*.h files.



Dr. Douglas C. Schmidt                       Professor and Associate Chair
Electrical Engineering and Computer Science  TEL: (615) 343-8197
Vanderbilt University                        WEB: www.dre.vanderbilt.edu/~schmidt
Nashville, TN 37203                          NET: d.schmidt at vanderbilt.edu

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