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

> * Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)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_int
sleep(secs)
u_int secs;
{
struct timeval nt, 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(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026