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From "William A. Rowe, Jr." <wr...@lnd.com>
Subject RE: Buffered file I/O & thread safety
Date Sun, 11 Jun 2000 19:43:53 GMT
> From: Greg Stein [mailto:gstein@lyra.org]
> Sent: Sunday, June 11, 2000 2:27 PM
> 
> On Sun, Jun 11, 2000 at 11:07:28PM +1000, Brian Havard wrote:
> > Some benchmarking clearly shows (at least on OS/2, I expect 
> other platforms
> > to be similar) that the mutex lock used to make the 
> buffered file I/O
> > thread safe is quite expensive (a lock & unlock for every 
> byte read in some
> > cases). It is also usually not necessary. The only 
> situation it's needed is
> > when the same ap_file_t object is used in multiple threads 
> (EG a log file
> > used by all threads). 
> > 
> > In the case of mod_include or config file reading only 1 
> thread will ever
> > touch the ap_file_t so a serious speed boost can be 
> achieved by turning off
> > the locking. To this end I propose adding a flag value for 
> ap_open() to
> > indicate if the handle needs to be thread safe, say APR_MT.
> > 
> > Any objections?
> 
> Sounds like a good plan. Default should be "safe", meaning 
> locking. Add the APR_MT to get the speed.

Uh... then let's try APR_BUFF_NO_MTLOCK or something MUCH
clearer that they are doing something potentially bad :-)

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