raffaele.ronchi@xxxxxxxxx wrote: > I have installed Fedora Core2 (Kernel 2.6.5-1.358smp) on a system > with Xeon MP processors. I ran the same program (multithreaded) on > this system and compared the results Vs. what obtained on the same > hardware running RH Advanced Server 3.0 (Kernel 2.4.21-9.ELsmp). Four points: 1. As other people have said, it's very difficult to provide meaningful answers when all we know is that the program is multi-threaded. Does it use NPTL threads, for example? 2. It looks as though your program spends a lot of time in kernel mode. Kernel mode switches are relatively slow on Fedora 2 SMP, because it has the 4G/4G kernel mode enabled by default. This forces the MMU to throw away its TLB on each kernel / user context switch, and your program looks like it has a lot of them. To get around this, you would have to recompile your kernel. Under "Processor type and features" and "High Memory Support", choose the *lowest* amount of memory you need. 3. It is known that in some areas 2.6 will perform worse than 2.4. Usually this is aimed at providing a more consistent environment where performance won't become spectacularly bad as you approach the worst- case scenarios. If you can identify particular areas of your program that have slowed down, and can provide a test case to the Linux Kernel Mailing List, mentioning the word "regression", I'm sure they'd be very interested. 4. When posting to a mailing list, it is normally considered polite to keep your lines under 80 characters (under 72 is often considered good practice). Hope this helps, James. -- E-mail address: james@ | "Never trust a species that grins all the time. westexe.demon.co.uk | It's up to something." | (Terry Pratchett on dolphins)