[Ace-users] [ace-users] pread/pwrite implementation for ACE_HAS_WINNT4 performance

[Johnny Willemsen]

Hi,

The current code doesn't check for ACE_HAS_WINNT4, so:

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

$ACE_ROOT/PROBLEM-REPORT-FORM
$TAO_ROOT/PROBLEM-REPORT-FORM

or in

$ACE_ROOT/BUG-REPORT-FORM
$TAO_ROOT/BUG-REPORT-FORM

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
to.
 
Regards,

Johnny Willemsen
Remedy IT
Postbus 101
2650 AC  Berkel en Rodenrijs
The Netherlands
www.theaceorb.nl / www.remedy.nl  

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<daniel.schenk at schiller.ch> wrote in message
news:<1193739147.174354.145830 at 22g2000hsm.googlegroups.com>...
> Hi
> 
> in ace\OS_NS_unistd.cpp the ACE_WIN32 implementation of ACE_OS::pread
> uses
> 1. ACE_OS_GUARD to synchronize access
> 2. gets the current file pointer, set it to the desired offset and
> restores it after reading
> 
> Both should be unnecessary if ACE_HAS_WINNT4 is defined.
> Because ::ReadFile is used with an OVERLAPPED structure. ::ReadFile
> will set the offset internally, which is passed inside the OVERLAPPED
> structure. Therefore there will be no need for synchronization by
> ACE_OS_GUARD.
> This will mean that the current implementation for  ACE_HAS_WINNT4
> unnecessarily calls  SetFilePointer 3 times and locks, which will of
> course slow down the performance.
> The same will be true for ACE_OS::pwrite.
> 
> Please correct me, if I'm wrong. Otherwise I would appreciate if you
> could change the code.
> 
> best regards
> 
> Daniel Schenk
>