Chances are, they're Intel Xeon hyperthreaded CPUs, which essentially make themselves look like two processors each. In an SMP machine, this can cause problems with threaded applications since the kernel (unable to distinguish between a real and "virtual" processor) might put several threads on the same physical processor. A user used to these threads running on separate CPUs would notice a performance difference. One thing you might try is turning off hyperthreading in the BIOS. You'll see a slight performance loss on single-threaded apps, but your kernel will no longer group threads on the same processor. Michael Wimpee System Administrator On Tue, Jul 27, 2004 at 04:07:42PM +0100, Andrew.Bridgeman@xxxxxxxxxxxxxx wrote: > I have recently rebuilt a Linux machine ( Redhat 7.3 ). I have just noticed > that when i do the top command it shows 4 CPU'S, the strange thing is that > i only have 2 CPU's in the machine. I had a e-mail from one of my users > complaining about jobs running slower than expected on this machine as per > text below. Can someone tell me why this is the case and how i get my > machine back to showing 2 CPU's! > > job running 20% slower on lin14 than expected. 4 cpus were being monitored > on lin14 instead of 2. > > Regards > > Andrew Bridgeman > IT Systems Engineer > Corus Automotive > IARC Building > University of Warwick > Coventry > CV47AL > Tel: +44 (0)2476 241262 > > > ********************************************************************** > This transmission is confidential and must not be used or disclosed by > anyone other than the intended recipient. Neither Corus Group Plc nor > any of its subsidiaries can accept any responsibility for any use or > misuse of the transmission by anyone. > ********************************************************************** > > > > -- > redhat-list mailing list > unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe > https://www.redhat.com/mailman/listinfo/redhat-list > -- redhat-list mailing list unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe https://www.redhat.com/mailman/listinfo/redhat-list
