I have an application that is licensed by the processor, and it sees the HT processor as if it were real, costly....
That said, we did some quick tests, turn HT off, turn it back on, and for this app it was nearly linear performance gains, YMMV, depending on applications. This was on Windows 2003 server, which claims to support/exploit HT fully. The reading that I did boiled down to, test it yourself, but expect about 70% + scalability, if you aren't paying for licenses for software based on "CPUs" then it seems to me that most of the time you'll do well to leave it enabled. Isn't it frequently better to run 2x as many jobs/threads even if they take a little bit longer to process? Depends on the app, your config, etc. Kevin On Wed, 2004-10-13 at 18:01, Jeremy Portzer wrote: > On Wed, 2004-10-13 at 17:47, John Franklin wrote: > > > One of the big issues with HT is that it looks like SMP to HT-unaware > > kernels. The difference between SMP and HT is the shared resources on > > the chip. When moving a process to a second CPU (core), an HT-unaware > > kernel may blow the CPU cache, move the process to the second core > > thinking it's a physically separate CPU, and refill the CPU cache. An > > HT-aware kernel will move the process w/o blowing the cache. > > > > Would it therefore be prudent to turn off HT if your application is > memory-intensive? Is it even possible to turn off HT (e.g. BIOS > setting)? If I can turn it off, I guess I could try to do some > benchmarks with my particular application... > > I'm using kernel 2.4.21 with Red Hat's modifications, on CentOS 3.3. > > Jeremy -- +--------------------------------------------------------------+ If you never see anything that offends you, you aren't living in a free society Kim Campbell - Former Canadian Prime Minister -- TriLUG mailing list : http://www.trilug.org/mailman/listinfo/trilug TriLUG Organizational FAQ : http://trilug.org/faq/ TriLUG Member Services FAQ : http://members.trilug.org/services_faq/ TriLUG PGP Keyring : http://trilug.org/~chrish/trilug.asc
