Subject Re: SS CPU_AFFINITY and Hyperthreading with Windows 2003 SE
Author Adam
It would be quicker for you to test it yourself than to wait for a
response from knowledgable users who probably haven't used anything
earlier than 1.5 in the last 18 months - 2 years.

There (was / is) an issue where windows would continuously switch the
CPU that the firebird process is running on, rather than farming out
the different threads to the different available CPUs. If this is the
case, it should be quite apparant. The CPU usage will jump up to 100%
for significant amounts of time.

All CPU affinity does is to tell Windows to only schedule the firebird
process on the particular CPU you lock it to.

Note that this is only an issue to Superserver. Classic server
launches a different process for each connection, so windows is able
to put different connections on different CPUs.

Some people have noticed a similar phenomenon with hyperthreading, as
well as another one where it delays the connection time significantly.

I do not know when these issues first arose, nor when they were solved
and if in fact they are solved. I have never had to disable HT or set
CPU affinity to get mine to play nice, but then again, I use win 2003
and if you heard that fixes it, then I guess that explains something.

The easiest way to test is to set the CPU affinity, restart the
service, and run some tests.

Then unset the CPU affinity, restart the service, and run some tests.
Allowing for expected variances and that in some cases the multi cpu
will be slower, is there a significant measurable difference?

Repeat the test enabling and disabling HT in BIOS.


--- In, "robert_difalco"
<rdifalco@t...> wrote:
> Anyone have any ideas on this one? Can 1.0.3 make use of
> multiprocessors? Should I use CPU_AFFINITY on a multi-proc Windows
> 2003 machine or on a Windows 2003 machine with Hyperthreading?
> --- In, "robert_difalco"
> <rdifalco@t...> wrote:
> > I know that Windows 2003 resolved some Hyperthreading issues so that
> > it is no longer suggested to disable hyperthreading in the BIOS,
> > however, I am not sure if we should be leaving CPU_AFFINITY commented
> > out or if we should set it to a single processor. Thoughts? And yes,
> > this is 1.0.3. :(
> >
> > R.