Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com Delivered-To: mailing list cygwin AT cygwin DOT com Message-ID: <40EBF4C7.B2E27B6D@dessent.net> Date: Wed, 07 Jul 2004 06:04:07 -0700 From: Brian Dessent Organization: My own little world... MIME-Version: 1.0 To: cygwin AT cygwin DOT com Subject: Re: two instances of a.exe on dual processor - still only 50% performance References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-IsSubscribed: yes Reply-To: cygwin AT cygwin DOT com mathias DOT wagner AT philips DOT com wrote: > Many thanks for this tip. I tried it out and indeed there is a "Set > Affinity" option in the Taskmanager. Apparently, this option lets you > assign one or more of the 4 virtual processors to a particular task. (W2K > seems to have this concept of virtual processors, I am no expert at all > here). But it doesn't change a thing. still 50% are spent on Idle mode... You see 4 CPUs because of HyperThreading. A HT CPU registers with the OS as two CPUs, but it's not. Only in certain circumstances can it run two threads concurrently (such as performing an integer and floating operation at the same time.) Thus 50% CPU usage means that your system is fully loaded. On a HT system you've got to double all the CPU usage percentages for it to make sense. Occasionally you might see it surpass 50%, which would mean that the hyperthreading is particularly suited to whatever combination of instructions is being executed and it's using the CPU more efficiently. Brian -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/