Tom Lane wrote:
> Dave Cramer <pg@fastcrypt.com> writes:
> > I tried increasing the NUM_SPINS to 1000 and it works better.
>
> Doesn't surprise me. The value of 100 is about right on the assumption
> that the spinlock instruction per se is not too much more expensive than
> any other instruction. What I was seeing from oprofile suggested that
> the spinlock instruction cost about 100x more than an ordinary
> instruction :-( ... so maybe 200 or so would be good on a Xeon.
>
> > This is certainly heading in the right direction ? Although it looks
> > like it is highly dependent on the system you are running on.
>
> Yeah. I don't know a reasonable way to tune this number automatically
> for particular systems ... but at the very least we'd need to find a way
> to distinguish uniprocessor from multiprocessor, because on a
> uniprocessor the optimal value is surely 1.
Have you looked at the code pointed to by our TODO item:
* Add code to detect an SMP machine and handle spinlocks accordingly
from distributted.net, http://www1.distributed.net/source,
in client/common/cpucheck.cpp
For BSDOS it has:
#if (CLIENT_OS == OS_FREEBSD) || (CLIENT_OS == OS_BSDOS) || \
(CLIENT_OS == OS_OPENBSD) || (CLIENT_OS == OS_NETBSD)
{ /* comment out if inappropriate for your *bsd - cyp (25/may/1999) */
int ncpus; size_t len = sizeof(ncpus);
int mib[2]; mib[0] = CTL_HW; mib[1] = HW_NCPU;
if (sysctl( &mib[0], 2, &ncpus, &len, NULL, 0 ) == 0)
//if (sysctlbyname("hw.ncpu", &ncpus, &len, NULL, 0 ) == 0)
cpucount = ncpus;
}
and I can confirm that on my computer it works:
hw.ncpu = 2
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
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