Date: Mon, 7 Jul 2003 15:54:59 +0200 From: Matthias Andree <matthias.andree@gmx.de> To: current@freebsd.org Subject: Re: /dev/shm Message-ID: <20030707135459.GH10021@merlin.emma.line.org> In-Reply-To: <3F097719.8030301@gmx.net> References: <3F08B199.3050409@comcast.net> <3F08B79B.2040805@gmx.net> <20030707001443.GA1530@invisible-island.net> <20030707002347.GC5141@aurema.com> <20030706203440.D89894@vhost101.his.com> <3F08C4FD.8010107@gmx.net> <m3el12lf91.fsf@merlin.emma.line.org> <3F09663D.9020200@gmx.net> <20030707123707.GA18750@saltmine.radix.net> <3F097719.8030301@gmx.net>
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On Mon, 07 Jul 2003, Marcin Dalecki wrote: > The point is that this is one of the reasons why the top command in > question takes a lot of relative CPU time under Linux. Some > "faster" versions of procps utils try to cache data but the trade off > is simply the fact that the results are not 100% accurate. Top data is not accurate (I though that was obvious ;-). It's an obsolete snapshot the very moment it's printed to your console, and I bet it changes as you read with a lot of implementations because no-one wants to beat the big kernel lock on the process list just because some user happens to run top, might be a nice DoS otherwise, fork-bombing top... If you want accurate data, use a kernel debugger with remote interface and make sure the machine does nothing except servicing the debugger interface. > I tought this was obvious? Why do I care? 0.58user 0.89system 1:00.91elapsed 2%CPU -- on a 266 MHz Pentium-II, Linux 2.4, 5 years old, with 190 processes. The box idles 73% of the time it's up, there's _ample_ CPU power left. -- Matthias Andree
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