Date: Mon, 25 May 2009 21:34:05 +0200 From: Peter Boosten <peter@boosten.org> To: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> Cc: Yuri <yuri@rawbw.com>, Scott Bennett <bennett@cs.niu.edu>, freebsd-questions@freebsd.org, utisoft@gmail.com Subject: Re: How can this 'top' command output make sense? Load over 7 and total CPU use ~5% Message-ID: <EEB4E0E6-E903-4FCD-A583-2A17ACE9E902@boosten.org> In-Reply-To: <alpine.BSF.2.00.0905252119520.41069@wojtek.tensor.gdynia.pl> References: <200905241315.n4ODFB96007801@mp.cs.niu.edu> <alpine.BSF.2.00.0905242021440.33060@wojtek.tensor.gdynia.pl> <b79ecaef0905250104p55c302cdh102202d1a06a389b@mail.gmail.com> <alpine.BSF.2.00.0905251013500.36458@wojtek.tensor.gdynia.pl> <b79ecaef0905250133n5cd641dv6ca8e088f8fa2f33@mail.gmail.com> <4A1A58FA.60303@boosten.org> <alpine.BSF.2.00.0905251912000.40022@wojtek.tensor.gdynia.pl> <C9B964A3-BE91-4518-B13C-EE28282FD810@boosten.org> <alpine.BSF.2.00.0905252107590.40989@wojtek.tensor.gdynia.pl> <1932D812-03CF-48AF-A306-669C39862EB7@boosten.org> <alpine.BSF.2.00.0905252119520.41069@wojtek.tensor.gdynia.pl>
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On 25 mei 2009, at 21:24, Wojciech Puchar wrote: >> >> The CPU will perform the same, whether at 10% utilization, or at >> 100% utilization, the system however won't. >> That's the difference between load and utilization. > > still don't understand you. > > CPU will not perform the same at 10% utilization, it will perform 10 > times less than at 100% utilization. *sigh* The CPU = "Central Processing Unit" will perform it's calculations at so many megahertz while at 10% utilization or at 100% utilization. The entire machine is only performing at 10% of its capacity, in your statement above. Load = burden. Under heavy _load_ the _machine_ will become sluggish, but the CPU will still be performing at the same megahertz speed. You cannot put the CPU under load (=burden), since it was designed to perform at 100% (actually it can be, if the queue length gets too large, and then it's called load, but that's not being done in top). The fact that the CPU has to wait for some I/O will not influence the performance of the CPU, but to the entire machine. > > > CPU load == CPU utilization == how big percentage of time CPU (or > CPUs by average) are doing anything except being in idle loop or hlt/ > waiting for interrupt. > it's exactly the same words in that context. > > > load average is how much processes (by average) is not doing > calculations because something is not yet available and depends of > computer resources(*) - like CPU time, disk I/O results etc.. > Actually, it's a combination of both running and waiting processes. > (*) - for example waiting on tty read is not calculated to load > average as it's depends on human not computer. Peter -- http://www.boosten.org
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