Date: Wed, 14 Mar 2001 18:51:25 -0800 From: Alfred Perlstein <bright@wintelcom.net> To: David Scheidt <dscheidt@tumbolia.com> Cc: chat@freebsd.org Subject: Re: Disk I/O problem in 4.3-BETA Message-ID: <20010314185125.T29888@fw.wintelcom.net> In-Reply-To: <Pine.BSF.4.21.0103141941300.38966-100000@shell-2.enteract.com>; from dscheidt@tumbolia.com on Wed, Mar 14, 2001 at 07:44:49PM -0600 References: <20010314154323.O29888@fw.wintelcom.net> <Pine.BSF.4.21.0103141941300.38966-100000@shell-2.enteract.com>
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* David Scheidt <dscheidt@tumbolia.com> [010314 17:44] wrote: > On Wed, 14 Mar 2001, Alfred Perlstein wrote: > > :* Iain Templeton <iain@research.canon.com.au> [010314 14:54] wrote: > :> On Mon, 12 Mar 2001, Alfred Perlstein wrote: > :It's a common starvation problem. > : > :Imagine an elevator that always goes to the nearest requested floor > :instead of making almost complete up then down sweeps. > : > :At quit time there's a good chance you'll never hit the lobby > :because the elevator keeps going to the nearest floor which is > :unlikely to be the lobby once it gets high up enough. > : > :Matt explained that Linux had this "feature" to reduce disk seeking > :for a short period, finally someone with algorithm experience stood > :up and smacked enough people around such that it got changed to > :the proper elevator algorithm. > > HP introduced this problem (I think it was somewhat subtler than the way > you've laid it out, though) into HP/UX 10.20 at some point. It meant that > ls would take minutes(!!) to produce output on one of the boxes I ran, if > it was being pounded on in a certain way. It's been fixed for a long time, > though. That's really funny, about 4-5 years ago I talked to someone who had just finished interviewing a potential candidate who had been working in the HPUX devel team (i think). And talked about a "a weird problem when we have lots of IO". Does that even come close to the same time period? -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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