Date: Fri, 19 Oct 2001 06:26:36 -0700 From: Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca> To: Ryan Thompson <ryan@sasknow.com> Cc: "jslivko@4evermail.com" <jslivko@4evermail.com>, freebsd-questions@FreeBSD.ORG Subject: Re: Loads on a Web/Shell Server Message-ID: <200110191326.f9JDQmf34019@cwsys.cwsent.com> In-Reply-To: Your message of "Thu, 18 Oct 2001 20:51:55 MDT." <Pine.BSF.4.21.0110182037080.211-100000@ren.sasknow.com>
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In message <Pine.BSF.4.21.0110182037080.211-100000@ren.sasknow.com>, Ryan Thomp son writes: > jslivko@4evermail.com wrote to stable@FreeBSD.ORG: > > > Hello, > > > > I have a shell/web hosting company (4EverMail Hosting Services) and I > > have a little bit of a problem with the loads on my machine. I am > > hosting a few IRC servers, eggdrop bots and a few apache websites > > (mainly my own), and the loads are already at 0.15 and so on. > > Load averages confuse a lot of people. 0.15 is quite low. On the server I > am logged in to: It is true that load averages are confusing at first. Once it is understood how the system calculates the load average, it can be a useful tuning tool. Take for example the example: > 8:37PM up 205 days, 17:52, 6 users, load averages: 2.44, 2.51, 2.45 If the load average was chronic and vmstat showed that the CPU was at 100%, this would be an indication that a faster CPU might be required. If on the other hand very little CPU was being used or most of it was system state, another area to look at would be I/O. Is there a disk that is too busy? Or, the load average might be indicative of a memory problem. Is the scan rate or page out rate too high? Are we seeing a lot of page reclaims? Generally the load average tells us that there might be a shortage or misalignment of resources. It's a simple way to get a feel for how well the system is doing without getting into a detailed analysis of the metrics that will ultimately point us in the right direction. It's akin to looking up at the sky and saying "it might just rain today", then looking at the detailed weather charts to confirm or deny one's suspicion (that being the detailed analysis after looking at the load average). For example, on an Alpha system running Tru64-UNIX with a load average of > 1. If the system is performing well, you can bet the system is CPU bound. If on an Alpha system with a load average > 1 is performing sluggishly, you can bet the problem is I/O. FreeBSD systems can take load averages of 6 or 7 before they appear sluggish. On Sun Sparc systems a load average of 3 to 5 seems to be the borderline. Having said all that, a load average of 12, for example, caused by CPU bound processes that have been niced will appear to run quite nicely. Having an intimate familiarity of the hardware, software, and applications running on your system and how it normally runs goes a long way to understanding load average on a particular system. What may be a high load average on one system may not necessarily be a high load average on another system running a different mix of applications. Regards, Phone: (250)387-8437 Cy Schubert Fax: (250)387-5766 Team Leader, Sun/Alpha Team Internet: Cy.Schubert@osg.gov.bc.ca Open Systems Group, ITSD Ministry of Management Services Province of BC To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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