Re: RE: [COMMITTERS] pgsql/src/backend/access/transam ( xact.c xlog.c)

> * Bruce Momjian <pgman@candle.pha.pa.us> [001116 14:02]:
> > > > This sounds like an interesting approach, yes.
> > > Question: Is sleep(0) guaranteed to at least give up control? 
> > > 
> > > The way I read my UnixWare 7's man page, it might not, since alarm(0)
> > > just cancels the alarm...
> > 
> > Well, it certainly is a kernel call, and most OS's re-evaluate on kernel
> > call return.
> BUT, do we know for sure that sleep(0) is not optimized in the library
> to just return? 

We can only do our best here. I think guessing whether other backends
are _about_ to commit is pretty shaky, and sleeping every time is a
waste.  This seems the cleanest.

Funny you should mention the optimization.  I just checked BSDI and saw:u_intsleep(secs)    u_int secs;{    struct
timevalnt, ot;    long diff;    int rc;    if (secs == 0)        return (0);
 

So maybe we need another _fake_ kernel call, or a select/usleep with a
very small value.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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